@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 <math.h>
#include <time.h>
#include "vpx_scale/yv12config.h"
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ EXTRA_INCLUDES

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ HELPERS
extern double vp8_calc_ssim
(
    YV12_BUFFER_CONFIG *source,
    YV12_BUFFER_CONFIG *dest,
    int lumamask,
    double *weight
);

extern double vp8_ssim
(
    const unsigned char *img1,
    const unsigned char *img2,
    int stride_img1,
    int stride_img2,
    int width,
    int height
);

struct detect_buffer {
    char buf[4];
    size_t buf_read;
    size_t position;
};

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;
}

double ssim_yuv(unsigned char *ptr_ref, 
                unsigned char *ptr_deg,
                int w,
                int h,
                double *weight) 
{
    /* insert ref and deg into YV12_BUFFER_CONFIG structs
     * and calculate SSIM for this frame
     */
    
    YV12_BUFFER_CONFIG ref, deg;
    
    ref.y_width = w;
    ref.y_height = h;
    ref.y_stride = w;
    ref.uv_width = w/2;
    ref.uv_height = h/2;
    ref.uv_stride = w/2;
    ref.y_buffer = ptr_ref;
    ref.u_buffer = ptr_ref + w*h;
    ref.v_buffer = ptr_ref + w*h + (w*h)/4;
    /* do not need the rest of the struct parameters; leave them as is */
    
    deg.y_width = w;
    deg.y_height = h;
    deg.y_stride = w;
    deg.uv_width = w/2;
    deg.uv_height = h/2;
    deg.uv_stride = w/2;
    deg.y_buffer = ptr_deg;
    deg.u_buffer = ptr_deg + w*h;
    deg.v_buffer = ptr_deg + w*h + (w*h)/4;
    
    return vp8_calc_ssim(&ref, &deg, 1, weight);
}

void write_and_eval_frame(unsigned char *img_buf,
                         int w,
                         int h,
                         FILE *outfile,
                         FILE *reffile,
                         double *sum_ssim,
                         double *sum_weight)
{
    /* write frame in img to output file and calculate SSIM */
    int img_sz = (w*h*3)/2;
    unsigned char *ref_buf = NULL;
    double temp_ssim;
    double weight = 0.0;
    
    if(!img_buf || !outfile || !reffile) 
        die("Failure in write_and_eval_frame");
    
    if(fwrite(img_buf, 1, img_sz, outfile) != img_sz)
        die("Could not write to file");
    
    /* Read next frame from reference file */
    ref_buf = (unsigned char *) malloc(img_sz);
    if(!ref_buf)
        die("Error allocating memory");

    if(fread(ref_buf, 1, img_sz, reffile) != img_sz)
        die("Failed to read complete reference frame");

    /* Calculate SSIM */
    
    temp_ssim = ssim_yuv(ref_buf, img_buf, 
                         w, h, &weight);
    *sum_ssim += temp_ssim * weight;
    *sum_weight += weight;
    
    free(ref_buf);    
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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!=5 && argc != 6)
    die("Usage: %s <infile> <outfile> <reffile> <N-M|N/M|L,S>\n", 
        argv[0]);
{
    char *nptr;
    n = strtol(argv[4], &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[4]);
}
seed = (m > 0) ? m : (unsigned int)time(NULL);
srand(seed);thrown_frame = 0;
printf("Seed: %u\n", seed);

if(!(reffile = fopen(argv[3], "rb")))
    die("Failed to open %s for reading", argv[3]);

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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;
unsigned char   *last_yuv_buf = NULL;
int              last_sz = 0;
int              last_alloc_sz = 0;
unsigned char   *temp_last = NULL;
int              expected_decode = 1;
FILE            *reffile, *sttfile;
unsigned char   *ref_yuv_buf = NULL;
int              ref_sz = 0;
int              ref_alloc_sz = 0;
double           sum_ssim = 0.0, sum_weight = 0.0;
double           total_ssim;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ DECODE
/* Decode the frame, use frame_cnt as user-specific data */
if(vpx_codec_decode(&codec, frame, frame_sz, NULL /*(void *) frame_cnt*/, 0))
    die_codec(&codec, "Failed to decode frame");
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ DECODE


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ GET_FRAME
while((img = vpx_codec_get_frame(&codec, &iter))) {
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ GET_FRAME


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PROCESS_DX
/* Check if we are missing frames */
while(/*((int) img->user_priv)*/ frame_cnt > expected_decode) {
    write_and_eval_frame(last_yuv_buf,
                         img->d_w,
                         img->d_h,
                         outfile,
                         reffile,
                         &sum_ssim,
                         &sum_weight);
                         
    expected_decode++;
    }

expected_decode++; 

/* Check size of last_yuv_buf */
if(last_alloc_sz < (img->d_w * img->d_h * 3) / 2) {
    /* Re-allocate */
    if(last_yuv_buf) {
        free(last_yuv_buf);
        last_yuv_buf = NULL;
    }
    last_alloc_sz = (img->d_w * img->d_h * 3) / 2;
    last_yuv_buf = (unsigned char *) malloc(last_alloc_sz);
    last_sz = 0;
}

/* First, write new frame to last_yuv_buf */
temp_last = last_yuv_buf;
last_sz = 0;
for(plane=0; plane < 3; plane++) {
    unsigned char *buf =img->planes[plane];

    for(y=0; y<img->d_h >> (plane?1:0); y++) {
        memcpy(temp_last, buf, img->d_w >> (plane?1:0));
        temp_last += img->d_w >> (plane?1:0);
        last_sz += img->d_w >> (plane?1:0);
        buf += img->stride[plane];
    }
}

/* Then, write it to file and calculate SSIM*/
write_and_eval_frame(last_yuv_buf,
                     img->d_w,
                     img->d_h,
                     outfile,
                     reffile,
                     &sum_ssim,
                     &sum_weight);
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PROCESS_DX


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ DESTROY

total_ssim = sum_ssim / sum_weight;
printf("SSIM = %f\n", total_ssim);

if(!(sttfile = fopen("loss.stt", "at")))
    die("Failed to open loss.stt for writing");
fprintf(sttfile, "lossparam \tSSIM\n");
fprintf(sttfile, "%s\t%f\n", argv[4], total_ssim);
fclose(sttfile);

if(last_yuv_buf)
    free(last_yuv_buf);

if(vpx_codec_destroy(&codec))
    die_codec(&codec, "Failed to destroy codec");
    
fclose(reffile);
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ DESTROY