vpx/examples/postproc.txt
Deb Mukherjee 87aa846b47 Multiframe quality enhancement postprocessing
Adds a multiframe postprocessing module to enhance the quality of
certain frames that are coded at lower quality than preceding frames.
The module can be invoked from the commandline by use of the --mfqe
option, and will be most beneficial for enhancing the quality of
frames decoded using scalable patterns.

Uses the vp8_variance_var16x16 and vp8_variance_sad16x16 function
pointers to compute SAD and Variance of blocks.

Change-Id: Id73d2a6e3572d07f9f8e36bbce00a4fc5ffd8961
2012-01-05 10:21:48 -08:00

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@TEMPLATE decoder_tmpl.c
Postprocessing Decoder
======================
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ INTRODUCTION
This example adds postprocessing to the simple decoder loop.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ INTRODUCTION
Initializing Postprocessing
---------------------------
You must inform the codec that you might request postprocessing at
initialization time. This is done by passing the VPX_CODEC_USE_POSTPROC
flag to `vpx_codec_dec_init`. If the codec does not support
postprocessing, this call will return VPX_CODEC_INCAPABLE. For
demonstration purposes, we also fall back to default initialization if
the codec does not provide support.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ DEC_INIT
/* Initialize codec */
res = vpx_codec_dec_init(&codec, interface, NULL,
VPX_CODEC_USE_POSTPROC);
if(res == VPX_CODEC_INCAPABLE) {
printf("NOTICE: Postproc not supported by %s\n",
vpx_codec_iface_name(interface));
res = vpx_codec_dec_init(&codec, interface, NULL, flags);
}
if(res)
die_codec(&codec, "Failed to initialize decoder");
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ DEC_INIT
Using Adaptive Postprocessing
-----------------------------
VP6 provides "adaptive postprocessing." It will automatically select the
best postprocessing filter on a frame by frame basis based on the amount
of time remaining before the user's specified deadline expires. The
special value 0 indicates that the codec should take as long as
necessary to provide the best quality frame. This example gives the
codec 15ms (15000us) to return a frame. Remember that this is a soft
deadline, and the codec may exceed it doing its regular processing. In
these cases, no additional postprocessing will be done.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ DECODE
/* Decode the frame with 15ms deadline */
if(vpx_codec_decode(&codec, frame, frame_sz, NULL, 15000))
die_codec(&codec, "Failed to decode frame");
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ DECODE
Codec Specific Postprocessing Controls
--------------------------------------
Some codecs provide fine grained controls over their built-in
postprocessors. VP8 is one example. The following sample code toggles
postprocessing on and off every 15 frames.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PRE_DECODE
#if CONFIG_VP8_DECODER
if(frame_cnt%30 == 1) {
vp8_postproc_cfg_t pp = {0, 0, 0};
if(vpx_codec_control(&codec, VP8_SET_POSTPROC, &pp))
die_codec(&codec, "Failed to turn off postproc");
} else if(frame_cnt%30 == 16) {
vp8_postproc_cfg_t pp = {VP8_DEBLOCK | VP8_DEMACROBLOCK | VP8_MFQE, 4, 0};
if(vpx_codec_control(&codec, VP8_SET_POSTPROC, &pp))
die_codec(&codec, "Failed to turn on postproc");
};
#endif
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PRE_DECODE