Added configure option to enable error-concealment. Disabled by default.

Change-Id: I94580a5ecb13520195ea2b8a10ca11bb5a01d2a6

configure

@@ -37,6 +37,7 @@ Advanced options:
   ${toggle_multithread}           multithreaded encoding and decoding.
   ${toggle_spatial_resampling}    spatial sampling (scaling) support
   ${toggle_realtime_only}         enable this option while building for real-time encoding
+  ${toggle_error_concealment}     enable this option to get a decoder which is able to conceal losses
   ${toggle_runtime_cpu_detect}    runtime cpu detection
   ${toggle_shared}                shared library support
   ${toggle_small}                 favor smaller size over speed
@@ -249,6 +250,7 @@ CONFIG_LIST="
     static_msvcrt
     spatial_resampling
     realtime_only
+    error_concealment
     shared
     small
     arm_asm_detok
@@ -289,6 +291,7 @@ CMDLINE_SELECT="
     mem_tracker
     spatial_resampling
     realtime_only
+    error_concealment
     shared
     small
     arm_asm_detok

examples.mk

@@ -77,6 +77,11 @@ GEN_EXAMPLES-$(CONFIG_ENCODERS) += decode_with_drops.c
 endif
 decode_with_drops.GUID           = CE5C53C4-8DDA-438A-86ED-0DDD3CDB8D26
 decode_with_drops.DESCRIPTION    = Drops frames while decoding
+ifeq ($(CONFIG_DECODERS),yes)
+GEN_EXAMPLES-$(CONFIG_ENCODERS) += decode_with_partial_drops.c
+endif
+decode_partial_with_drops.GUID           = CE5C53C4-8DDA-438A-86ED-0DDD3CDB8D27
+decode_partial_with_drops.DESCRIPTION    = Drops parts of frames while decoding
 GEN_EXAMPLES-$(CONFIG_ENCODERS) += error_resilient.c
 error_resilient.GUID             = DF5837B9-4145-4F92-A031-44E4F832E00C
 error_resilient.DESCRIPTION      = Error Resiliency Feature

examples/decode_with_partial_drops.txt

@@ -0,0 +1,213 @@
+@TEMPLATE decoder_tmpl.c
+Decode With Drops Example
+=========================
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ INTRODUCTION
+This is an example utility which drops a series of frames, as specified
+on the command line. This is useful for observing the error recovery
+features of the codec.
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ INTRODUCTION
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ EXTRA_INCLUDES
+#include <time.h>
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ EXTRA_INCLUDES
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ HELPERS
+struct parsed_header
+{
+    char key_frame;
+    int version;
+    char show_frame;
+    int first_part_size;
+};
+
+int next_packet(struct parsed_header* hdr, int pos, int length, int mtu)
+{
+    int size = 0;
+    int remaining = length - pos;
+    /* Uncompressed part is 3 bytes for P frames and 10 bytes for I frames */
+    int uncomp_part_size = (hdr->key_frame ? 10 : 3);
+    /* number of bytes yet to send from header and the first partition */
+    int remainFirst = uncomp_part_size + hdr->first_part_size - pos;
+    if (remainFirst > 0)
+    {
+        if (remainFirst <= mtu)
+        {
+            size = remainFirst;
+        }
+        else
+        {
+            size = mtu;
+        }
+
+        return size;
+    }
+
+    /* second partition; just slot it up according to MTU */
+    if (remaining <= mtu)
+    {
+        size = remaining;
+        return size;
+    }
+    return mtu;
+}
+
+void throw_packets(unsigned char* frame, int* size, int loss_rate, int* thrown, int* kept)
+{
+    unsigned char loss_frame[256*1024];
+    int pkg_size = 1;
+    int count = 0;
+    int pos = 0;
+    int loss_pos = 0;
+    struct parsed_header hdr;
+    unsigned int tmp;
+    int mtu = 100;
+
+    if (*size < 3)
+    {
+        return;
+    }
+    putc('|', stdout);
+    /* parse uncompressed 3 bytes */
+    tmp = (frame[2] << 16) | (frame[1] << 8) | frame[0];
+    hdr.key_frame = !(tmp & 0x1); /* inverse logic */
+    hdr.version = (tmp >> 1) & 0x7;
+    hdr.show_frame = (tmp >> 4) & 0x1;
+    hdr.first_part_size = (tmp >> 5) & 0x7FFFF;
+
+    /* don't drop key frames */
+    if (hdr.key_frame)
+    {
+        int i;
+        *kept = *size/mtu + ((*size % mtu > 0) ? 1 : 0); /* approximate */
+        for (i=0; i < *kept; i++)
+            putc('.', stdout);
+        return;
+    }
+
+    while ((pkg_size = next_packet(&hdr, pos, *size, mtu)) > 0)
+    {
+        int loss_event = ((rand() + 1.0)/(RAND_MAX + 1.0) < loss_rate/100.0);
+        if (*thrown == 0 && !loss_event)
+        {
+            memcpy(loss_frame + loss_pos, frame + pos, pkg_size);
+            loss_pos += pkg_size;
+            (*kept)++;
+            putc('.', stdout);
+        }
+        else
+        {
+            (*thrown)++;
+            putc('X', stdout);
+        }
+        pos += pkg_size;
+    }
+    memcpy(frame, loss_frame, loss_pos);
+    memset(frame + loss_pos, 0, *size - loss_pos);
+    *size = loss_pos;
+}
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ HELPERS
+
+Usage
+-----
+This example adds a single argument to the `simple_decoder` example,
+which specifies the range or pattern of frames to drop. The parameter is
+parsed as follows:
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ USAGE
+if(argc!=4 && argc != 5)
+    die("Usage: %s <infile> <outfile> <N-M|N/M|L,S>\n", argv[0]);
+{
+    char *nptr;
+    n = strtol(argv[3], &nptr, 0);
+    mode = (*nptr == '\0' || *nptr == ',') ? 2 : (*nptr == '-') ? 1 : 0;
+
+    m = strtol(nptr+1, NULL, 0);
+    if((!n && !m) || (*nptr != '-' && *nptr != '/' &&
+        *nptr != '\0' && *nptr != ','))
+        die("Couldn't parse pattern %s\n", argv[3]);
+}
+seed = (m > 0) ? m : (unsigned int)time(NULL);
+srand(seed);thrown_frame = 0;
+printf("Seed: %u\n", seed);
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ USAGE
+
+
+Dropping A Range Of Frames
+--------------------------
+To drop a range of frames, specify the starting frame and the ending
+frame to drop, separated by a dash. The following command will drop
+frames 5 through 10 (base 1).
+
+  $ ./decode_with_drops in.ivf out.i420 5-10
+
+
+Dropping A Pattern Of Frames
+----------------------------
+To drop a pattern of frames, specify the number of frames to drop and
+the number of frames after which to repeat the pattern, separated by
+a forward-slash. The following command will drop 3 of 7 frames.
+Specifically, it will decode 4 frames, then drop 3 frames, and then
+repeat.
+
+  $ ./decode_with_drops in.ivf out.i420 3/7
+
+
+Extra Variables
+---------------
+This example maintains the pattern passed on the command line in the
+`n`, `m`, and `is_range` variables:
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ EXTRA_VARS
+int              n, m, mode;                                        //
+unsigned int     seed;
+int              thrown=0, kept=0;
+int              thrown_frame=0, kept_frame=0;
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ EXTRA_VARS
+
+
+Making The Drop Decision
+------------------------
+The example decides whether to drop the frame based on the current
+frame number, immediately before decoding the frame.
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PRE_DECODE
+/* Decide whether to throw parts of the frame or the whole frame
+   depending on the drop mode */
+thrown_frame = 0;
+kept_frame = 0;
+switch (mode)
+{
+case 0:
+    if (m - (frame_cnt-1)%m <= n)
+    {
+        frame_sz = 0;
+    }
+    break;
+case 1:
+    if (frame_cnt >= n && frame_cnt <= m)
+    {
+        frame_sz = 0;
+    }
+    break;
+case 2:
+    throw_packets(frame, &frame_sz, n, &thrown_frame, &kept_frame);
+    break;
+default: break;
+}
+if (mode < 2)
+{
+    if (frame_sz == 0)
+    {
+        putc('X', stdout);
+        thrown_frame++;
+    }
+    else
+    {
+        putc('.', stdout);
+        kept_frame++;
+    }
+}
+thrown += thrown_frame;
+kept += kept_frame;
+fflush(stdout);
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PRE_DECODE

examples/decoder_tmpl.c

@@ -42,6 +42,8 @@ static void die(const char *fmt, ...) {
 
 @DIE_CODEC
 
+@HELPERS
+
 int main(int argc, char **argv) {
     FILE            *infile, *outfile;
     vpx_codec_ctx_t  codec;

vp8/common/alloccommon.c

@@ -12,6 +12,7 @@
 #include "vpx_ports/config.h"
 #include "blockd.h"
 #include "vpx_mem/vpx_mem.h"
+#include "error_concealment.h"
 #include "onyxc_int.h"
 #include "findnearmv.h"
 #include "entropymode.h"
@@ -28,6 +29,9 @@ void vp8_update_mode_info_border(MODE_INFO *mi, int rows, int cols)
 
     for (i = 0; i < rows; i++)
     {
+        /* TODO(holmer): Bug? This updates the last element of each row
+         * rather than the border element!
+         */
         vpx_memset(&mi[i*cols-1], 0, sizeof(MODE_INFO));
     }
 }
@@ -44,9 +48,11 @@ void vp8_de_alloc_frame_buffers(VP8_COMMON *oci)
 
     vpx_free(oci->above_context);
     vpx_free(oci->mip);
+    vpx_free(oci->prev_mip);
 
     oci->above_context = 0;
     oci->mip = 0;
+    oci->prev_mip = 0;
 
 }
 
@@ -111,6 +117,16 @@ int vp8_alloc_frame_buffers(VP8_COMMON *oci, int width, int height)
 
     oci->mi = oci->mip + oci->mode_info_stride + 1;
 
+    /* allocate memory for last frame MODE_INFO array */
+    oci->prev_mip = vpx_calloc((oci->mb_cols + 1) * (oci->mb_rows + 1), sizeof(MODE_INFO));
+
+    if (!oci->prev_mip)
+    {
+        vp8_de_alloc_frame_buffers(oci);
+        return ALLOC_FAILURE;
+    }
+
+    oci->prev_mi = oci->prev_mip + oci->mode_info_stride + 1;
 
     oci->above_context = vpx_calloc(sizeof(ENTROPY_CONTEXT_PLANES) * oci->mb_cols, 1);
 

vp8/common/onyxc_int.h

@@ -140,6 +140,8 @@ typedef struct VP8Common
 
     MODE_INFO *mip; /* Base of allocated array */
     MODE_INFO *mi;  /* Corresponds to upper left visible macroblock */
+    MODE_INFO *prev_mip; /* MODE_INFO array 'mip' from last decoded frame */
+    MODE_INFO *prev_mi;  /* 'mi' from last frame (points into prev_mip) */
 
 
     INTERPOLATIONFILTERTYPE mcomp_filter_type;

vp8/decoder/dboolhuff.h

@@ -126,7 +126,7 @@ static void vp8dx_bool_decoder_fill(BOOL_DECODER *br) {
         for(shift = VP8_BD_VALUE_SIZE - 8 - ((_count) + 8); shift >= 0; ) \
         { \
             if((_bufptr) >= (_bufend)) { \
-                (_count) = VP8_LOTS_OF_BITS; \
+                (_count) += VP8_LOTS_OF_BITS; \
                 break; \
             } \
             (_count) += 8; \
@@ -209,18 +209,19 @@ static int vp8_decode_value(BOOL_DECODER *br, int bits)
 
 static int vp8dx_bool_error(BOOL_DECODER *br)
 {
-  /* Check if we have reached the end of the buffer.
-   *
-   * Variable 'count' stores the number of bits in the 'value' buffer,
-   * minus 8. So if count == 8, there are 16 bits available to be read.
-   * Normally, count is filled with 8 and one byte is filled into the
-   * value buffer. When we reach the end of the buffer, count is instead
-   * filled with VP8_LOTS_OF_BITS, 8 of which represent the last 8 real
-   * bits from the bitstream. So the last bit in the bitstream will be
-   * represented by count == VP8_LOTS_OF_BITS - 16.
-   */
-    if ((br->count > VP8_BD_VALUE_SIZE)
-        && (br->count <= VP8_LOTS_OF_BITS - 16))
+    /* Check if we have reached the end of the buffer.
+     *
+     * Variable 'count' stores the number of bits in the 'value' buffer, minus
+     * 8. The top byte is part of the algorithm, and the remainder is buffered
+     * to be shifted into it. So if count == 8, the top 16 bits of 'value' are
+     * occupied, 8 for the algorithm and 8 in the buffer.
+     *
+     * When reading a byte from the user's buffer, count is filled with 8 and
+     * one byte is filled into the value buffer. When we reach the end of the
+     * data, count is additionally filled with VP8_LOTS_OF_BITS. So when
+     * count == VP8_LOTS_OF_BITS - 1, the user's data has been exhausted.
+     */
+    if ((br->count > VP8_BD_VALUE_SIZE) && (br->count < VP8_LOTS_OF_BITS))
     {
        /* We have tried to decode bits after the end of
         * stream was encountered.

vp8/decoder/decodemv.c

@@ -251,6 +251,7 @@ void vp8_mb_mode_mv_init(VP8D_COMP *pbi)
     vp8_reader *const bc = & pbi->bc;
     MV_CONTEXT *const mvc = pbi->common.fc.mvc;
 
+    pbi->mvs_corrupt_from_mb = -1;
     pbi->prob_skip_false = 0;
     if (pbi->common.mb_no_coeff_skip)
         pbi->prob_skip_false = (vp8_prob)vp8_read_literal(bc, 8);
@@ -412,7 +413,7 @@ void vp8_read_mb_modes_mv(VP8D_COMP *pbi, MODE_INFO *mi, MB_MODE_INFO *mbmi,
 
                     do {
                         mi->bmi[ *fill_offset] = bmi;
-                      fill_offset++;
+                        fill_offset++;
 
                     }while (--fill_count);
                 }
@@ -543,12 +544,18 @@ void vp8_decode_mode_mvs(VP8D_COMP *pbi)
 
         while (++mb_col < pbi->common.mb_cols)
         {
+            int mb_num = mb_row * pbi->common.mb_cols + mb_col;
             /*vp8_read_mb_modes_mv(pbi, xd->mode_info_context, &xd->mode_info_context->mbmi, mb_row, mb_col);*/
             if(pbi->common.frame_type == KEY_FRAME)
                 vp8_kfread_modes(pbi, mi, mb_row, mb_col);
             else
                 vp8_read_mb_modes_mv(pbi, mi, &mi->mbmi, mb_row, mb_col);
 
+            /* look for corruption */
+            if (vp8dx_bool_error(&pbi->bc) && mb_num < pbi->mvs_corrupt_from_mb)
+                pbi->mvs_corrupt_from_mb = mb_num;
+
+
             mi++;       /* next macroblock */
         }
 

vp8/decoder/decodframe.c

@@ -27,6 +27,7 @@
 
 #include "decodemv.h"
 #include "extend.h"
+#include "error_concealment.h"
 #include "vpx_mem/vpx_mem.h"
 #include "idct.h"
 #include "dequantize.h"
@@ -176,11 +177,21 @@ void clamp_mvs(MACROBLOCKD *xd)
 
 }
 
-void vp8_decode_macroblock(VP8D_COMP *pbi, MACROBLOCKD *xd)
+void vp8_decode_macroblock(VP8D_COMP *pbi, MACROBLOCKD *xd, unsigned int mb_idx)
 {
     int eobtotal = 0;
     int i, do_clamp = xd->mode_info_context->mbmi.need_to_clamp_mvs;
 
+    /* TODO(holmer): change when we have MB level error tracking
+     * The residuals may not match the predicted signal when a macroblock is
+     * corrupted due to previous losses. Should we try to add the residual
+     * anyway, or just throw it away? Should test this on a couple of files.
+     */
+    if (pbi->ec_enabled && mb_idx >= pbi->mvs_corrupt_from_mb)
+    {
+        xd->mode_info_context->mbmi.mb_skip_coeff = 1;
+    }
+
     if (xd->mode_info_context->mbmi.mb_skip_coeff)
     {
         vp8_reset_mb_tokens_context(xd);
@@ -333,6 +344,7 @@ void vp8_decode_mb_row(VP8D_COMP *pbi,
     int dst_fb_idx = pc->new_fb_idx;
     int recon_y_stride = pc->yv12_fb[ref_fb_idx].y_stride;
     int recon_uv_stride = pc->yv12_fb[ref_fb_idx].uv_stride;
+    int corrupt_partition = 0;
 
     vpx_memset(&pc->left_context, 0, sizeof(pc->left_context));
     recon_yoffset = mb_row * recon_y_stride * 16;
@@ -347,6 +359,28 @@ void vp8_decode_mb_row(VP8D_COMP *pbi,
 
     for (mb_col = 0; mb_col < pc->mb_cols; mb_col++)
     {
+        /* Distance of Mb to the various image edges.
+         * These are specified to 8th pel as they are always compared to values that are in 1/8th pel units
+         */
+        xd->mb_to_left_edge = -((mb_col * 16) << 3);
+        xd->mb_to_right_edge = ((pc->mb_cols - 1 - mb_col) * 16) << 3;
+
+        if (xd->mode_info_context->mbmi.ref_frame == INTRA_FRAME &&
+            corrupt_partition)
+        {
+            /* We have an intra block with corrupt coefficients,
+             * better to conceal with an inter block. Interpolate MVs
+             * from neighboring MBs.
+             */
+            /* TODO(holmer): We will fail to conceal an intra block with missing
+             * coefficients if it's the first block with missing coefficients,
+             * since the bool dec error detection is done after reconstruction.
+             */
+            vp8_interpolate_motion(xd,
+                                   mb_row, mb_col,
+                                   pc->mb_rows, pc->mb_cols,
+                                   pc->mode_info_stride);
+        }
 
         if (xd->mode_info_context->mbmi.mode == SPLITMV || xd->mode_info_context->mbmi.mode == B_PRED)
         {
@@ -357,12 +391,6 @@ void vp8_decode_mb_row(VP8D_COMP *pbi,
             }
         }
 
-        /* Distance of Mb to the various image edges.
-         * These are specified to 8th pel as they are always compared to values that are in 1/8th pel units
-         */
-        xd->mb_to_left_edge = -((mb_col * 16) << 3);
-        xd->mb_to_right_edge = ((pc->mb_cols - 1 - mb_col) * 16) << 3;
-
         xd->dst.y_buffer = pc->yv12_fb[dst_fb_idx].y_buffer + recon_yoffset;
         xd->dst.u_buffer = pc->yv12_fb[dst_fb_idx].u_buffer + recon_uvoffset;
         xd->dst.v_buffer = pc->yv12_fb[dst_fb_idx].v_buffer + recon_uvoffset;
@@ -395,10 +423,11 @@ void vp8_decode_mb_row(VP8D_COMP *pbi,
         else
         pbi->debugoutput =0;
         */
-        vp8_decode_macroblock(pbi, xd);
+        vp8_decode_macroblock(pbi, xd, mb_row * pc->mb_cols + mb_col);
 
         /* check if the boolean decoder has suffered an error */
-        xd->corrupted |= vp8dx_bool_error(xd->current_bc);
+        corrupt_partition = vp8dx_bool_error(xd->current_bc);
+        xd->corrupted |= corrupt_partition;
 
         recon_yoffset += 16;
         recon_uvoffset += 8;
@@ -469,8 +498,8 @@ static void setup_token_decoder(VP8D_COMP *pbi,
             partition_size = user_data_end - partition;
         }
 
-        if (partition + partition_size > user_data_end
-            || partition + partition_size < partition)
+        if (!pbi->ec_enabled && (partition + partition_size > user_data_end
+            || partition + partition_size < partition))
             vpx_internal_error(&pc->error, VPX_CODEC_CORRUPT_FRAME,
                                "Truncated packet or corrupt partition "
                                "%d length", i + 1);
@@ -584,63 +613,87 @@ int vp8_decode_frame(VP8D_COMP *pbi)
     pc->yv12_fb[pc->new_fb_idx].corrupted = 0;
 
     if (data_end - data < 3)
-        vpx_internal_error(&pc->error, VPX_CODEC_CORRUPT_FRAME,
-                           "Truncated packet");
-    pc->frame_type = (FRAME_TYPE)(data[0] & 1);
-    pc->version = (data[0] >> 1) & 7;
-    pc->show_frame = (data[0] >> 4) & 1;
-    first_partition_length_in_bytes =
-        (data[0] | (data[1] << 8) | (data[2] << 16)) >> 5;
-    data += 3;
-
-    if (data + first_partition_length_in_bytes > data_end
-        || data + first_partition_length_in_bytes < data)
-        vpx_internal_error(&pc->error, VPX_CODEC_CORRUPT_FRAME,
-                           "Truncated packet or corrupt partition 0 length");
-    vp8_setup_version(pc);
-
-    if (pc->frame_type == KEY_FRAME)
     {
-        const int Width = pc->Width;
-        const int Height = pc->Height;
-
-        /* vet via sync code */
-        if (data[0] != 0x9d || data[1] != 0x01 || data[2] != 0x2a)
-            vpx_internal_error(&pc->error, VPX_CODEC_UNSUP_BITSTREAM,
-                               "Invalid frame sync code");
-
-        pc->Width = (data[3] | (data[4] << 8)) & 0x3fff;
-        pc->horiz_scale = data[4] >> 6;
-        pc->Height = (data[5] | (data[6] << 8)) & 0x3fff;
-        pc->vert_scale = data[6] >> 6;
-        data += 7;
-
-        if (Width != pc->Width  ||  Height != pc->Height)
+        if (pbi->ec_enabled)
         {
-            int prev_mb_rows = pc->mb_rows;
+            /* Declare the missing frame as an inter frame since it will
+               be handled as an inter frame when we have estimated its
+               motion vectors. */
+            pc->frame_type = INTER_FRAME;
+            pc->version = 0;
+            pc->show_frame = 1;
+            first_partition_length_in_bytes = 0;
+        }
+        else
+        {
+            vpx_internal_error(&pc->error, VPX_CODEC_CORRUPT_FRAME,
+                               "Truncated packet");
+        }
+    }
+    else
+    {
+        pc->frame_type = (FRAME_TYPE)(data[0] & 1);
+        pc->version = (data[0] >> 1) & 7;
+        pc->show_frame = (data[0] >> 4) & 1;
+        first_partition_length_in_bytes =
+            (data[0] | (data[1] << 8) | (data[2] << 16)) >> 5;
+        data += 3;
 
-            if (pc->Width <= 0)
+        if (!pbi->ec_enabled && (data + first_partition_length_in_bytes > data_end
+            || data + first_partition_length_in_bytes < data))
+            vpx_internal_error(&pc->error, VPX_CODEC_CORRUPT_FRAME,
+                               "Truncated packet or corrupt partition 0 length");
+        vp8_setup_version(pc);
+
+        if (pc->frame_type == KEY_FRAME)
+        {
+            const int Width = pc->Width;
+            const int Height = pc->Height;
+
+            /* vet via sync code */
+            if (!pbi->ec_enabled &&
+                (data[0] != 0x9d || data[1] != 0x01 || data[2] != 0x2a))
+                vpx_internal_error(&pc->error, VPX_CODEC_UNSUP_BITSTREAM,
+                                   "Invalid frame sync code");
+
+            pc->Width = (data[3] | (data[4] << 8)) & 0x3fff;
+            pc->horiz_scale = data[4] >> 6;
+            pc->Height = (data[5] | (data[6] << 8)) & 0x3fff;
+            pc->vert_scale = data[6] >> 6;
+            data += 7;
+
+            if (Width != pc->Width  ||  Height != pc->Height)
             {
-                pc->Width = Width;
-                vpx_internal_error(&pc->error, VPX_CODEC_CORRUPT_FRAME,
-                                   "Invalid frame width");
-            }
+                int prev_mb_rows = pc->mb_rows;
 
-            if (pc->Height <= 0)
-            {
-                pc->Height = Height;
-                vpx_internal_error(&pc->error, VPX_CODEC_CORRUPT_FRAME,
-                                   "Invalid frame height");
-            }
+                if (pc->Width <= 0)
+                {
+                    pc->Width = Width;
+                    vpx_internal_error(&pc->error, VPX_CODEC_CORRUPT_FRAME,
+                                       "Invalid frame width");
+                }
 
-            if (vp8_alloc_frame_buffers(pc, pc->Width, pc->Height))
-                vpx_internal_error(&pc->error, VPX_CODEC_MEM_ERROR,
-                                   "Failed to allocate frame buffers");
+                if (pc->Height <= 0)
+                {
+                    pc->Height = Height;
+                    vpx_internal_error(&pc->error, VPX_CODEC_CORRUPT_FRAME,
+                                       "Invalid frame height");
+                }
+
+                if (vp8_alloc_frame_buffers(pc, pc->Width, pc->Height))
+                    vpx_internal_error(&pc->error, VPX_CODEC_MEM_ERROR,
+                                       "Failed to allocate frame buffers");
+
+                if (vp8_alloc_overlap_lists(pbi))
+                    vpx_internal_error(&pc->error, VPX_CODEC_MEM_ERROR,
+                                       "Failed to allocate overlap lists for "
+                                       "error concealment");
 
 #if CONFIG_MULTITHREAD
-            if (pbi->b_multithreaded_rd)
-                vp8mt_alloc_temp_buffers(pbi, pc->Width, prev_mb_rows);
+                if (pbi->b_multithreaded_rd)
+                    vp8mt_alloc_temp_buffers(pbi, pc->Width, prev_mb_rows);
 #endif
+            }
         }
     }
 
@@ -862,6 +915,12 @@ int vp8_decode_frame(VP8D_COMP *pbi)
 
     vp8_decode_mode_mvs(pbi);
 
+    if (pbi->ec_enabled &&
+            pbi->mvs_corrupt_from_mb < (unsigned int)pc->mb_cols * pc->mb_rows)
+    {
+        vp8_estimate_missing_mvs(pbi);
+    }
+
     vpx_memset(pc->above_context, 0, sizeof(ENTROPY_CONTEXT_PLANES) * pc->mb_cols);
 
     vpx_memcpy(&xd->block[0].bmi, &xd->mode_info_context->bmi[0], sizeof(B_MODE_INFO));

vp8/decoder/ec_types.h

@@ -0,0 +1,40 @@
+/*
+ *  Copyright (c) 2011 The WebM project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef VP8_DEC_EC_TYPES_H
+#define VP8_DEC_EC_TYPES_H
+
+#define MAX_OVERLAPS 16
+
+typedef struct
+{
+    int overlap;
+    B_MODE_INFO *bmi;
+    MV_REFERENCE_FRAME ref_frame;
+} OVERLAP_NODE;
+
+typedef struct
+{
+    /* TODO(holmer): This array should be exchanged for a linked list */
+    OVERLAP_NODE overlaps[MAX_OVERLAPS];
+} B_OVERLAP;
+
+typedef struct
+{
+    B_OVERLAP overlaps[16];
+} MB_OVERLAP;
+
+typedef struct
+{
+    MV mv;
+    MV_REFERENCE_FRAME ref_frame;
+} EC_BLOCK;
+
+#endif /* VP8_DEC_EC_TYPES_H */

vp8/decoder/error_concealment.c

@@ -0,0 +1,612 @@
+/*
+ *  Copyright (c) 2011 The WebM project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "error_concealment.h"
+#include "onyxd_int.h"
+#include "vpx_mem/vpx_mem.h"
+
+#include <assert.h>
+
+#define MIN(x,y) (((x)<(y))?(x):(y))
+#define MAX(x,y) (((x)>(y))?(x):(y))
+
+#define FLOOR(x,q) ((x) & -(1 << (q)))
+
+#define NUM_NEIGHBORS 20
+
+typedef struct ec_position
+{
+    int row;
+    int col;
+} EC_POS;
+
+/*
+ * Regenerate the table in Matlab with:
+ * x = meshgrid((1:4), (1:4));
+ * y = meshgrid((1:4), (1:4))';
+ * W = round((1./(sqrt(x.^2 + y.^2))*2^7));
+ * W(1,1) = 0;
+ */
+static const int weights_q7[5][5] = {
+       {  0,   128,    64,    43,    32 },
+       {128,    91,    57,    40,    31 },
+       { 64,    57,    45,    36,    29 },
+       { 43,    40,    36,    30,    26 },
+       { 32,    31,    29,    26,    23 }
+};
+
+static int vp8_need_to_clamp_mv(MV *mv,
+                         int mb_to_left_edge,
+                         int mb_to_right_edge,
+                         int mb_to_top_edge,
+                         int mb_to_bottom_edge)
+{
+    return (mv->col < mb_to_left_edge) ||
+           (mv->col > mb_to_right_edge) ||
+           (mv->row < mb_to_top_edge) ||
+           (mv->row > mb_to_bottom_edge);
+}
+
+int vp8_alloc_overlap_lists(VP8D_COMP *pbi)
+{
+    if (pbi->overlaps != NULL)
+    {
+        vpx_free(pbi->overlaps);
+        pbi->overlaps = NULL;
+    }
+    pbi->overlaps = vpx_calloc(pbi->common.mb_rows * pbi->common.mb_cols,
+                               sizeof(MB_OVERLAP));
+    vpx_memset(pbi->overlaps, 0,
+               sizeof(MB_OVERLAP) * pbi->common.mb_rows * pbi->common.mb_cols);
+    if (pbi->overlaps == NULL)
+        return -1;
+    return 0;
+}
+
+void vp8_de_alloc_overlap_lists(VP8D_COMP *pbi)
+{
+    if (pbi->overlaps != NULL)
+    {
+        vpx_free(pbi->overlaps);
+        pbi->overlaps = NULL;
+    }
+}
+
+void vp8_assign_overlap(OVERLAP_NODE* overlaps,
+                        B_MODE_INFO *bmi,
+                        MV_REFERENCE_FRAME ref_frame,
+                        int overlap)
+{
+    int i;
+    if (overlap <= 0)
+        return;
+    for (i = 0; i < MAX_OVERLAPS; i++)
+    {
+        if (overlaps[i].bmi == NULL)
+        {
+            overlaps[i].bmi = bmi;
+            overlaps[i].ref_frame = ref_frame;
+            overlaps[i].overlap = overlap;
+            break;
+        }
+    }
+}
+
+int vp8_block_overlap(int b1_row, int b1_col, int b2_row, int b2_col)
+{
+    const int int_top = MAX(b1_row, b2_row); // top
+    const int int_left = MAX(b1_col, b2_col); // left
+    const int int_right = MIN(b1_col + (4<<3), b2_col + (4<<3)); // right
+    const int int_bottom = MIN(b1_row + (4<<3), b2_row + (4<<3)); // bottom
+    return (int_bottom - int_top) * (int_right - int_left);
+}
+
+void vp8_calculate_overlaps_mb(B_OVERLAP *b_overlaps, B_MODE_INFO *bmi,
+                               MV_REFERENCE_FRAME ref_frame,
+                               int new_row, int new_col,
+                               int mb_row, int mb_col,
+                               int first_blk_row, int first_blk_col)
+{
+    /* Find the blocks within this MB which are overlapped by bmi and
+     * calculate and assign overlap for each of those blocks. */
+
+    /* Block coordinates relative the upper-left block */
+    const int rel_ol_blk_row = first_blk_row - mb_row * 4;
+    const int rel_ol_blk_col = first_blk_col - mb_col * 4;
+    /* If the block partly overlaps any previous MB, these coordinates
+     * can be < 0. We don't want to access blocks in previous MBs.
+     */
+    const int blk_idx = MAX(rel_ol_blk_row,0) * 4 + MAX(rel_ol_blk_col,0);
+    /* Upper left overlapping block */
+    B_OVERLAP *b_ol_ul = &(b_overlaps[blk_idx]);
+
+    /* Calculate and assign overlaps for all blocks in this MB
+     * which the motion compensated block overlaps
+     */
+    /* Avoid calculating overlaps for blocks in later MBs */
+    int end_row = MIN(4 + mb_row * 4 - first_blk_row, 2);
+    int end_col = MIN(4 + mb_col * 4 - first_blk_col, 2);
+    int row, col;
+
+    /* Check if new_row and new_col are evenly divisible by 4 (Q3),
+     * and if so we shouldn't check neighboring blocks
+     */
+    if (new_row >= 0 && (new_row & 0x1F) == 0)
+        end_row = 1;
+    if (new_col >= 0 && (new_col & 0x1F) == 0)
+        end_col = 1;
+
+    /* Check if the overlapping block partly overlaps a previous MB
+     * and if so, we're overlapping fewer blocks in this MB.
+     */
+    if (new_row < (mb_row*16)<<3)
+        end_row = 1;
+    if (new_col < (mb_col*16)<<3)
+        end_col = 1;
+
+    for (row = 0; row < end_row; ++row)
+    {
+        for (col = 0; col < end_col; ++col)
+        {
+            /* input in Q3, result in Q6 */
+            const int overlap = vp8_block_overlap(new_row, new_col,
+                                                  (((first_blk_row + row) *
+                                                      4) << 3),
+                                                  (((first_blk_col + col) *
+                                                      4) << 3));
+            vp8_assign_overlap(b_ol_ul[row * 4 + col].overlaps,
+                               bmi,
+                               ref_frame,
+                               overlap);
+        }
+    }
+}
+
+void vp8_calculate_overlaps(MB_OVERLAP *overlap_ul,
+                            int mb_rows, int mb_cols,
+                            B_MODE_INFO *bmi,
+                            MV_REFERENCE_FRAME ref_frame,
+                            int b_row, int b_col)
+{
+    MB_OVERLAP *mb_overlap;
+    int row, col, rel_row, rel_col;
+    int new_row, new_col;
+    int new_row_pos, new_col_pos;
+    int end_row, end_col;
+    int overlap_b_row, overlap_b_col;
+    int overlap_mb_row, overlap_mb_col;
+    int i;
+    B_MODE_INFO *obmi;
+    int overlap;
+
+    if (ref_frame == INTRA_FRAME)
+        return;
+
+    /* mb subpixel position */
+    row = (4 * b_row) << 3; /* Q3 */
+    col = (4 * b_col) << 3; /* Q3 */
+
+    /* reverse compensate for motion */
+    new_row = row - bmi->mv.as_mv.row;
+    new_col = col - bmi->mv.as_mv.col;
+
+    if (new_row >= ((16*mb_rows) << 3) || new_col >= ((16*mb_cols) << 3))
+    {
+        /* the new block ended up outside the frame */
+        return;
+    }
+
+    if (new_row <= (-4 << 3) || new_col <= (-4 << 3))
+    {
+        /* outside the frame */
+        return;
+    }
+    /* overlapping block's position in blocks */
+    overlap_b_row = FLOOR(new_row / 4, 3) >> 3;
+    overlap_b_col = FLOOR(new_col / 4, 3) >> 3;
+
+    /* overlapping block's MB position in MBs
+     * operations are done in Q3
+     */
+    overlap_mb_row = FLOOR((overlap_b_row << 3) / 4, 3) >> 3;
+    overlap_mb_col = FLOOR((overlap_b_col << 3) / 4, 3) >> 3;
+
+    end_row = MIN(mb_rows - overlap_mb_row, 2);
+    end_col = MIN(mb_cols - overlap_mb_col, 2);
+
+    /* Don't calculate overlap for MBs we don't overlap */
+    /* Check if the new block row starts at the last block row of the MB */
+    if (abs(new_row - ((16*overlap_mb_row) << 3)) < ((3*4) << 3))
+        end_row = 1;
+    /* Check if the new block col starts at the last block col of the MB */
+    if (abs(new_col - ((16*overlap_mb_col) << 3)) < ((3*4) << 3))
+        end_col = 1;
+
+    /* find the MB(s) this block is overlapping */
+    for (rel_row = 0; rel_row < end_row; ++rel_row)
+    {
+        for (rel_col = 0; rel_col < end_col; ++rel_col)
+        {
+            if (overlap_mb_row + rel_row < 0 ||
+                overlap_mb_col + rel_col < 0)
+                continue;
+            mb_overlap = overlap_ul + (overlap_mb_row + rel_row) * mb_cols +
+                 overlap_mb_col + rel_col;
+
+            vp8_calculate_overlaps_mb(mb_overlap->overlaps, bmi, ref_frame,
+                                      new_row, new_col,
+                                      overlap_mb_row + rel_row,
+                                      overlap_mb_col + rel_col,
+                                      overlap_b_row + rel_row,
+                                      overlap_b_col + rel_col);
+        }
+    }
+}
+
+MV_REFERENCE_FRAME vp8_largest_overlap_type(const B_OVERLAP *block_overlaps)
+{
+    int i, j;
+    int overlap_per_type[MAX_REF_FRAMES] = {0};
+    int largest_overlap = 0;
+    MV_REFERENCE_FRAME largest_overlap_type = LAST_FRAME;
+    for (i=0; i < 16; ++i)
+    {
+        const OVERLAP_NODE *overlaps = block_overlaps->overlaps;
+        for (j=0; j < MAX_OVERLAPS; ++j)
+        {
+            if (overlaps[j].bmi != NULL)
+            {
+                overlap_per_type[overlaps[j].ref_frame] += overlaps[j].overlap;
+                if (overlap_per_type[overlaps[j].ref_frame] > largest_overlap)
+                {
+                    largest_overlap = overlap_per_type[overlaps[j].ref_frame];
+                    largest_overlap_type = overlaps[j].ref_frame;
+                }
+                assert(overlaps[j].overlap < (16*16)<<6);
+            }
+        }
+        ++block_overlaps;
+    }
+    return largest_overlap_type;
+}
+
+void vp8_estimate_mv(const OVERLAP_NODE *overlaps, B_MODE_INFO *bmi,
+                                   MV_REFERENCE_FRAME type)
+{
+    int i;
+    int overlap_sum = 0;
+    int row_acc = 0;
+    int col_acc = 0;
+
+    bmi->mv.as_int = 0;
+    for (i=0; i < MAX_OVERLAPS; ++i)
+    {
+        if (overlaps[i].bmi != NULL &&
+            overlaps[i].ref_frame == type)
+        {
+            col_acc += overlaps[i].overlap * overlaps[i].bmi->mv.as_mv.col;
+            row_acc += overlaps[i].overlap * overlaps[i].bmi->mv.as_mv.row;
+            overlap_sum += overlaps[i].overlap;
+        }
+    }
+    if (overlap_sum > 0)
+    {
+        /* Q9 / Q6 = Q3 */
+        bmi->mv.as_mv.col = col_acc / overlap_sum;
+        bmi->mv.as_mv.row = row_acc / overlap_sum;
+        bmi->mode = NEW4X4;
+    }
+    else
+    {
+        bmi->mv.as_mv.col = 0;
+        bmi->mv.as_mv.row = 0;
+        bmi->mode = NEW4X4;
+    }
+}
+
+void vp8_estimate_mb_mvs(const B_OVERLAP *block_overlaps,
+                         MODE_INFO *mi,
+                         int mb_to_left_edge,
+                         int mb_to_right_edge,
+                         int mb_to_top_edge,
+                         int mb_to_bottom_edge)
+{
+    int i;
+    int non_zero_count = 0;
+    MV * const filtered_mv = &(mi->mbmi.mv.as_mv);
+    B_MODE_INFO * const bmi = mi->bmi;
+    filtered_mv->col = 0;
+    filtered_mv->row = 0;
+    for (i = 0; i < 16; ++i)
+    {
+        /* Estimate vectors for all blocks which are overlapped by this
+         * type
+         */
+        /* Interpolate/extrapolate the rest of the block's MVs */
+        vp8_estimate_mv(block_overlaps[i].overlaps, bmi + i,
+                mi->mbmi.ref_frame);
+        mi->mbmi.need_to_clamp_mvs = vp8_need_to_clamp_mv(&(bmi[i].mv.as_mv),
+                                                          mb_to_left_edge,
+                                                          mb_to_right_edge,
+                                                          mb_to_top_edge,
+                                                          mb_to_bottom_edge);
+        if (bmi[i].mv.as_int != 0)
+        {
+            ++non_zero_count;
+            filtered_mv->col += bmi[i].mv.as_mv.col;
+            filtered_mv->row += bmi[i].mv.as_mv.row;
+        }
+    }
+    if (non_zero_count > 0)
+    {
+        filtered_mv->col /= non_zero_count;
+        filtered_mv->row /= non_zero_count;
+    }
+}
+
+void vp8_estimate_missing_mvs(VP8D_COMP *pbi)
+{
+    VP8_COMMON * const pc = &pbi->common;
+    vp8_estimate_missing_mvs_ex(pbi->overlaps,
+                                pc->mi, pc->prev_mi,
+                                pc->mb_rows, pc->mb_cols,
+                                pbi->mvs_corrupt_from_mb);
+}
+
+void vp8_estimate_missing_mvs_ex(MB_OVERLAP *overlaps,
+                                 MODE_INFO *mi, MODE_INFO *prev_mi,
+                                 int mb_rows, int mb_cols,
+                                 unsigned int first_corrupt)
+{
+    const unsigned int num_mbs = mb_rows * mb_cols;
+    int mb_row, mb_col;
+    vpx_memset(overlaps, 0, sizeof(MB_OVERLAP) * mb_rows * mb_cols);
+    /* First calculate the overlaps for all blocks */
+    for (mb_row = 0; mb_row < mb_rows; ++mb_row)
+    {
+        for (mb_col = 0; mb_col < mb_cols; ++mb_col)
+        {
+            int sub_row;
+            int sub_col;
+            for (sub_row = 0; sub_row < 4; ++sub_row)
+            {
+                for (sub_col = 0; sub_col < 4; ++sub_col)
+                {
+                    vp8_calculate_overlaps(
+                                        overlaps, mb_rows, mb_cols,
+                                        &(prev_mi->bmi[sub_row * 4 + sub_col]),
+                                        prev_mi->mbmi.ref_frame,
+                                        4 * mb_row + sub_row,
+                                        4 * mb_col + sub_col);
+                }
+            }
+            ++prev_mi;
+        }
+        ++prev_mi;
+    }
+
+    mb_row = first_corrupt / mb_cols;
+    mb_col = first_corrupt - mb_row * mb_cols;
+    mi += mb_row*(mb_cols + 1) + mb_col;
+    /* Go through all macroblocks in the current image with missing MVs
+     * and calculate new MVs using the overlaps.
+     */
+    for (; mb_row < mb_rows; ++mb_row)
+    {
+        int mb_to_top_edge = -((mb_row * 16)) << 3;
+        int mb_to_bottom_edge = ((mb_rows - 1 - mb_row) * 16) << 3;
+        for (; mb_col < mb_cols; ++mb_col)
+        {
+            int mb_to_left_edge = -((mb_col * 16) << 3);
+            int mb_to_right_edge = ((mb_cols - 1 - mb_col) * 16) << 3;
+            int i;
+            MV_REFERENCE_FRAME type = LAST_FRAME;
+            int largest_overlap = 0;
+            const B_OVERLAP *block_overlaps =
+                    overlaps[mb_row*mb_cols + mb_col].overlaps;
+            /* Find largest overlap and its type */
+            mi->mbmi.ref_frame = vp8_largest_overlap_type(block_overlaps);
+            vp8_estimate_mb_mvs(block_overlaps,
+                                mi,
+                                mb_to_left_edge,
+                                mb_to_right_edge,
+                                mb_to_top_edge,
+                                mb_to_bottom_edge);
+            mi->mbmi.mode = SPLITMV;
+            mi->mbmi.uv_mode = DC_PRED;
+            mi->mbmi.partitioning = 3;
+            ++mi;
+        }
+        mb_col = 0;
+        ++mi;
+    }
+}
+
+static void assign_neighbor(EC_BLOCK *neighbor, MODE_INFO *mi, int block_idx)
+{
+    assert(mi->mbmi.ref_frame < MAX_REF_FRAMES);
+    neighbor->ref_frame = mi->mbmi.ref_frame;
+    neighbor->mv = mi->bmi[block_idx].mv.as_mv;
+}
+
+void vp8_find_neighboring_blocks(MODE_INFO *mi,
+                                 EC_BLOCK *neighbors,
+                                 int mb_row, int mb_col,
+                                 int mb_rows, int mb_cols,
+                                 int mi_stride)
+{
+    int i = 0;
+    int j;
+    if (mb_row > 0)
+    {
+        /* upper left */
+        if (mb_col > 0)
+            assign_neighbor(&neighbors[i], mi - mi_stride - 1, 15);
+        ++i;
+        /* above */
+        for (j = 12; j < 16; ++j, ++i)
+            assign_neighbor(&neighbors[i], mi - mi_stride, j);
+    }
+    else
+        i += 5;
+    if (mb_col < mb_cols - 1)
+    {
+        /* upper right */
+        if (mb_row > 0)
+            assign_neighbor(&neighbors[i], mi - mi_stride + 1, 12);
+        ++i;
+        /* right */
+        for (j = 0; j <= 12; j += 4, ++i)
+            assign_neighbor(&neighbors[i], mi + 1, j);
+    }
+    else
+        i += 5;
+    if (mb_row < mb_rows - 1)
+    {
+        /* lower right */
+        if (mb_col < mb_cols - 1)
+            assign_neighbor(&neighbors[i], mi + mi_stride + 1, 0);
+        ++i;
+        /* below */
+        for (j = 0; j < 4; ++j, ++i)
+            assign_neighbor(&neighbors[i], mi + mi_stride, j);
+    }
+    else
+        i += 5;
+    if (mb_col > 0)
+    {
+        /* lower left */
+        if (mb_row < mb_rows - 1)
+            assign_neighbor(&neighbors[i], mi + mi_stride - 1, 4);
+        ++i;
+        /* left */
+        for (j = 3; j < 16; j += 4, ++i)
+        {
+            assign_neighbor(&neighbors[i], mi - 1, j);
+        }
+    }
+    else
+        i += 5;
+    assert(i == 20);
+}
+
+MV_REFERENCE_FRAME vp8_dominant_ref_frame(EC_BLOCK *neighbors)
+{
+    /* Default to referring to "skip" */
+    MV_REFERENCE_FRAME dom_ref_frame = LAST_FRAME;
+    int max_ref_frame_cnt = 0;
+    int ref_frame_cnt[MAX_REF_FRAMES] = {0};
+    int i;
+    /* Count neighboring reference frames */
+    for (i = 0; i < NUM_NEIGHBORS; ++i)
+    {
+        if (neighbors[i].ref_frame < MAX_REF_FRAMES)
+            ++ref_frame_cnt[neighbors[i].ref_frame];
+    }
+    /* Find maximum */
+    for (i = 0; i < MAX_REF_FRAMES; ++i)
+    {
+        if (ref_frame_cnt[i] > max_ref_frame_cnt)
+        {
+            dom_ref_frame = i;
+            max_ref_frame_cnt = ref_frame_cnt[i];
+        }
+    }
+    return dom_ref_frame;
+}
+
+void vp8_interpolate_mvs(MACROBLOCKD *mb,
+                         EC_BLOCK *neighbors,
+                         MV_REFERENCE_FRAME dom_ref_frame)
+{
+    int row, col, i;
+    MODE_INFO * const mi = mb->mode_info_context;
+    /* Table with the position of the neighboring blocks relative the position
+     * of the upper left block of the current MB. Starting with the upper left
+     * neighbor and going to the right.
+     */
+    const EC_POS neigh_pos[NUM_NEIGHBORS] = {
+                                        {-1,-1}, {-1,0}, {-1,1}, {-1,2}, {-1,3},
+                                        {-1,4}, {0,4}, {1,4}, {2,4}, {3,4},
+                                        {4,4}, {4,3}, {4,2}, {4,1}, {4,0},
+                                        {4,-1}, {3,-1}, {2,-1}, {1,-1}, {0,-1}
+                                      };
+    for (row = 0; row < 4; ++row)
+    {
+        for (col = 0; col < 4; ++col)
+        {
+            int w_sum = 0;
+            int mv_row_sum = 0;
+            int mv_col_sum = 0;
+            MV * const mv = &(mi->bmi[row*4 + col].mv.as_mv);
+            for (i = 0; i < NUM_NEIGHBORS; ++i)
+            {
+                /* Calculate the weighted sum of neighboring MVs referring
+                 * to the dominant frame type.
+                 */
+                const int w = weights_q7[abs(row - neigh_pos[i].row)]
+                                        [abs(col - neigh_pos[i].col)];
+                if (neighbors[i].ref_frame != dom_ref_frame)
+                    continue;
+                w_sum += w;
+                /* Q7 * Q3 = Q10 */
+                mv_row_sum += w*neighbors[i].mv.row;
+                mv_col_sum += w*neighbors[i].mv.col;
+            }
+            if (w_sum > 0)
+            {
+                /* Avoid division by zero.
+                 * Normalize with the sum of the coefficients
+                 * Q3 = Q10 / Q7
+                 */
+                mv->row = mv_row_sum / w_sum;
+                mv->col = mv_col_sum / w_sum;
+                mi->bmi[row*4 + col].mode = NEW4X4;
+                mi->mbmi.need_to_clamp_mvs = vp8_need_to_clamp_mv(mv,
+                                                       mb->mb_to_left_edge,
+                                                       mb->mb_to_right_edge,
+                                                       mb->mb_to_top_edge,
+                                                       mb->mb_to_bottom_edge);
+            }
+        }
+    }
+}
+
+void vp8_interpolate_motion(MACROBLOCKD *mb,
+                        int mb_row, int mb_col,
+                        int mb_rows, int mb_cols,
+                        int mi_stride)
+{
+    /* Find relevant neighboring blocks */
+    EC_BLOCK neighbors[NUM_NEIGHBORS];
+    MV_REFERENCE_FRAME dom_ref_frame;
+    int i;
+    /* Initialize the array. MAX_REF_FRAMES is interpreted as "doesn't exist" */
+    for (i = 0; i < NUM_NEIGHBORS; ++i)
+    {
+        neighbors[i].ref_frame = MAX_REF_FRAMES;
+        neighbors[i].mv.row = neighbors[i].mv.col = 0;
+    }
+    vp8_find_neighboring_blocks(mb->mode_info_context,
+                                neighbors,
+                                mb_row, mb_col,
+                                mb_rows, mb_cols,
+                                mb->mode_info_stride);
+    /* Determine the dominant block type */
+    dom_ref_frame = vp8_dominant_ref_frame(neighbors);
+    /* Interpolate MVs for the missing blocks
+     * from the dominating MVs */
+    vp8_interpolate_mvs(mb, neighbors, dom_ref_frame);
+
+    mb->mode_info_context->mbmi.ref_frame = dom_ref_frame;
+    mb->mode_info_context->mbmi.mode = SPLITMV;
+    mb->mode_info_context->mbmi.uv_mode = DC_PRED;
+    mb->mode_info_context->mbmi.partitioning = 3;
+}

vp8/decoder/error_concealment.h

@@ -0,0 +1,112 @@
+/*
+ *  Copyright (c) 2011 The WebM project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+
+#ifndef ERROR_CONCEALMENT_H
+#define ERROR_CONCEALMENT_H
+
+#include "onyxd_int.h"
+#include "ec_types.h"
+
+/* Allocate memory for the overlap lists */
+int vp8_alloc_overlap_lists(VP8D_COMP *pbi);
+
+/* Deallocate the overlap lists */
+void vp8_de_alloc_overlap_lists(VP8D_COMP *pbi);
+
+/* Inserts a new overlap area value to the list of overlaps of a block */
+void vp8_assign_overlap(OVERLAP_NODE* overlaps,
+                        B_MODE_INFO *bmi,
+                        MV_REFERENCE_FRAME ref_frame,
+                        int overlap);
+
+/* Calculates the overlap area between two 4x4 squares, where the first
+ * square has its upper-left corner at (b1_row, b1_col) and the second
+ * square has its upper-left corner at (b2_row, b2_col). Doesn't
+ * properly handle squares which doesn't overlap.
+ */
+int vp8_block_overlap(int b1_row, int b1_col, int b2_row, int b2_col);
+
+/* Finds the reference frame type which has the largest overlapping area. */
+MV_REFERENCE_FRAME vp8_largest_overlap_type(const B_OVERLAP *block_overlaps);
+
+/* Calculates the overlap area for all blocks in a macroblock at position
+ * (mb_row, mb_col) in macroblocks, which are being overlapped by a given
+ * overlapping block at position (new_row, new_col) (in pixels, Q3). The
+ * first block being overlapped in the macroblock has position (first_blk_row,
+ * first_blk_col) in blocks relative the upper-left corner of the image.
+ */
+void vp8_calculate_overlaps_mb(B_OVERLAP *b_overlaps, B_MODE_INFO *bmi,
+                               MV_REFERENCE_FRAME ref_frame,
+                               int new_row, int new_col,
+                               int mb_row, int mb_col,
+                               int first_blk_row, int first_blk_col);
+
+/* Estimates a motion vector given the overlapping blocks' motion vectors.
+ * Filters out all overlapping blocks which doesn't refer to the correct
+ * reference frame type.
+ */
+void vp8_estimate_mv(const OVERLAP_NODE *overlaps, B_MODE_INFO *bmi,
+                     MV_REFERENCE_FRAME type);
+
+/* Estimates all motion vectors for a macroblock given the lists of
+ * overlaps for each block. Decides whether or not the MVs must be clamped.
+ */
+void vp8_estimate_mb_mvs(const B_OVERLAP *block_overlaps,
+                         MODE_INFO *mi,
+                         int mb_to_left_edge,
+                         int mb_to_right_edge,
+                         int mb_to_top_edge,
+                         int mb_to_bottom_edge);
+
+/* Estimate all missing motion vectors.
+ */
+void vp8_estimate_missing_mvs(VP8D_COMP *pbi);
+
+/* Estimate all missing motion vectors */
+void vp8_estimate_missing_mvs_ex(MB_OVERLAP *overlaps,
+                                 MODE_INFO *mi, MODE_INFO *prev_mi,
+                                 int mb_rows, int mb_cols,
+                                 unsigned int first_corrupt);
+
+/* Functions for spatial MV interpolation */
+
+/* Finds the neighboring blocks of a macroblocks. In the general case
+ * 20 blocks are found. If a fewer number of blocks are found due to
+ * image boundaries, those positions in the EC_BLOCK array are left "empty".
+ * The neighbors are enumerated with the upper-left neighbor as the first
+ * element, the second element refers to the neighbor to right of the previous
+ * neighbor, and so on. The last element refers to the neighbor below the first
+ * neighbor.
+ */
+void vp8_find_neighboring_blocks(MODE_INFO *mi,
+                                 EC_BLOCK *neighbors,
+                                 int mb_row, int mb_col,
+                                 int mb_rows, int mb_cols,
+                                 int mi_stride);
+
+/* Calculates which reference frame type is dominating among the neighbors */
+MV_REFERENCE_FRAME vp8_dominant_ref_frame(EC_BLOCK *neighbors);
+
+/* Interpolates all motion vectors for a macroblock from the neighboring blocks'
+ * motion vectors.
+ */
+void vp8_interpolate_mvs(MACROBLOCKD *mb,
+                         EC_BLOCK *neighbors,
+                         MV_REFERENCE_FRAME dom_ref_frame);
+
+/* Interpolates all motion vectors for a macroblock mb at position
+ * (mb_row, mb_col). */
+void vp8_interpolate_motion(MACROBLOCKD *mb,
+                            int mb_row, int mb_col,
+                            int mb_rows, int mb_cols,
+                            int mi_stride);
+
+#endif

vp8/decoder/onyxd_if.c

@@ -135,6 +135,13 @@ VP8D_PTR vp8dx_create_decompressor(VP8D_CONFIG *oxcf)
     vp8_init_detokenizer(pbi);
 #endif
     pbi->common.error.setjmp = 0;
+
+#if CONFIG_ERROR_CONCEALMENT
+    pbi->ec_enabled = 1;
+#else
+    pbi->ec_enabled = 0;
+#endif
+
     return (VP8D_PTR) pbi;
 }
 
@@ -150,6 +157,7 @@ void vp8dx_remove_decompressor(VP8D_PTR ptr)
     if (pbi->b_multithreaded_rd)
         vp8mt_de_alloc_temp_buffers(pbi, pbi->common.mb_rows);
 #endif
+    vp8_de_alloc_overlap_lists(pbi);
     vp8_decoder_remove_threads(pbi);
     vp8_remove_common(&pbi->common);
     vpx_free(pbi);
@@ -338,11 +346,14 @@ int vp8dx_receive_compressed_data(VP8D_PTR ptr, unsigned long size, const unsign
         */
         cm->yv12_fb[cm->lst_fb_idx].corrupted = 1;
 
-        /* Signal that we have no frame to show. */
-        cm->show_frame = 0;
+        if (!pbi->ec_enabled)
+        {
+            /* Signal that we have no frame to show. */
+            cm->show_frame = 0;
 
-        /* Nothing more to do. */
-        return 0;
+            /* Nothing more to do. */
+            return 0;
+        }
     }
 
 
@@ -407,6 +418,16 @@ int vp8dx_receive_compressed_data(VP8D_PTR ptr, unsigned long size, const unsign
         return retcode;
     }
 
+    /* copy mode info to storage for future error concealment */
+    if (pbi->common.prev_mip)
+    {
+        /* size allocated in vp8_alloc_frame_buffers() */
+        int size_of_mip = (pbi->common.mb_cols + 1) * (pbi->common.mb_rows + 1)
+            * sizeof(MODE_INFO);
+
+        memcpy(pbi->common.prev_mip, pbi->common.mip, size_of_mip);
+    }
+
     if (pbi->b_multithreaded_rd && cm->multi_token_partition != ONE_PARTITION)
     {
         if (swap_frame_buffers (cm))

vp8/decoder/onyxd_int.h

@@ -17,6 +17,7 @@
 #include "onyxc_int.h"
 #include "threading.h"
 #include "dequantize.h"
+#include "ec_types.h"
 
 typedef struct
 {
@@ -134,6 +135,10 @@ typedef struct VP8Decompressor
     vp8_prob prob_gf;
     vp8_prob prob_skip_false;
 
+    MB_OVERLAP *overlaps;
+    unsigned int mvs_corrupt_from_mb;
+    int ec_enabled;
+
 } VP8D_COMP;
 
 int vp8_decode_frame(VP8D_COMP *cpi);

vp8/vp8dx.mk

@@ -56,12 +56,14 @@ VP8_DX_SRCS-yes += decoder/decodemv.c
 VP8_DX_SRCS-yes += decoder/decodframe.c
 VP8_DX_SRCS-yes += decoder/dequantize.c
 VP8_DX_SRCS-yes += decoder/detokenize.c
+VP8_DX_SRCS-yes += decoder/error_concealment.c
 VP8_DX_SRCS-yes += decoder/generic/dsystemdependent.c
 VP8_DX_SRCS-yes += decoder/dboolhuff.h
 VP8_DX_SRCS-yes += decoder/decodemv.h
 VP8_DX_SRCS-yes += decoder/decoderthreading.h
 VP8_DX_SRCS-yes += decoder/dequantize.h
 VP8_DX_SRCS-yes += decoder/detokenize.h
+VP8_DX_SRCS-yes += decoder/error_concealment.h
 VP8_DX_SRCS-yes += decoder/onyxd_int.h
 VP8_DX_SRCS-yes += decoder/treereader.h
 VP8_DX_SRCS-yes += decoder/onyxd_if.c