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• sgienc : Support encoding high bit depth images with RLE

  20 novembre 2015, par Vittorio Giovara

  sgienc : Support encoding high bit depth images with RLE
  Signed-off-by : Vittorio Giovara <vittorio.giovara@gmail.com>
  

  • [DBH] Changelog
  • [DBH] libavcodec/sgienc.c

• How to encode a mp4 which has high quality,fast encode speed and low bitrate using FFmpeg API？

  8 septembre 2017, par OnlYet

  I have lots of ARGB binary data and need to encode them to a mp4 file using FFmpeg API.The most difficult things is to deal with the balance between quality,speed and bitrate.

  Below is two download links for mp4 files generated from the same ARGB data.

  • Generated through FFmpeg API : MP4 #1

  • Generated through FFmpeg command line : MP4 #2

  The mp4 generated through command line has high definition and low bitrate(745kbps) while the other has not enough high quality but high bitrate(1009kbps) I don’t know the parameters of the mp4 generated through command line but a part of my code is below :

   codec_ctx->codec_type = AVMEDIA_TYPE_VIDEO;
  
   codec_ctx->width = width;
  
   codec_ctx->height = height;
  
   codec_ctx->time_base.num = 1;
  
   codec_ctx->time_base.den = fps;
  
   stream->time_base = { 1, fps };
  
  if (!strcmp(out_fmt, "mp4"))
  
      {
  
          codec_ctx->codec_id = AV_CODEC_ID_H264;
  
          codec_ctx->bit_rate = 800 * 1000;
  
          codec_ctx->rc_max_rate = 800 * 1000;
  
          //codec_ctx->rc_min_rate = 200 * 1000;
  
          codec_ctx->rc_buffer_size = 500 * 1000;
  
          /* More gop_size less file size */
  
          codec_ctx->gop_size = 30;
  
          codec_ctx->max_b_frames = 3;
  
          /* Set relevant parameters of H264 */
  
          codec_ctx->qmin = 10;   //default 2
  
          codec_ctx->qmax = 31;   //default 31
  
          codec_ctx->max_qdiff = 4;
  
          codec_ctx->me_range = 16;   //default 0 
  
          codec_ctx->max_qdiff = 4;   //default 3 
  
          codec_ctx->qcompress = 0.6; //default 0.5
  
          ret = av_dict_set(dict, "profile", "high", 0);
  
          // Keep a balance between speed and quality when encoding
  
          ret = av_dict_set(dict, "preset", "superfast", 0);
  
          ret = av_dict_set(dict, "threads", "0", 0);
  
          ret = av_dict_set(dict, "crf", "26", 0);    
  
          // set delay time
  
          ret = av_dict_set(dict, "tune", "zerolatency", 0);
  
          return;
  
      }

  I know the parameters that affect video quality are mainly these :

  bitrate, "qp", "crf", gop_size, qmin and "preset".

  I tried to increase gop_size to decrease bitrate but mp4 quality became lower. I also found that the less crf, the more quality and the more bitrate. The less qmin,the more quality and the more bitrate. And preset a higher encode speed, the more bitrate.

  In fact, I want to set "preset" to ultrafast and set "crf" to 20 but the output mp4 will be larger.So why the mp4 generated through command line can be high quality but low bitrate ? How to set the parameters of AVCodecContext to generate a mp4 with high quality,low bitrate and high speed ?

  Supplementary notes ：
  The mp4 generated through command line stay low bitrate most of the time and higher bitrate sometimes but my mp4 is always stay relatively high bitrate. I think the point is to control the bitrate.

• Revision 7e40a55ef9 : Added high bitdepth sse2 transform functions Also removes some spurious changes

  24 octobre 2014, par Peter de Rivaz

  Changed Paths :
   Modify /test/dct16x16_test.cc

  
   Modify /test/dct32x32_test.cc

  
   Modify /test/fdct4x4_test.cc

  
   Modify /test/fdct8x8_test.cc

  
   Modify /vp9/common/vp9_blockd.h

  
   Modify /vp9/common/vp9_rtcd_defs.pl

  
   Modify /vp9/common/x86/vp9_idct_intrin_sse2.c

  
   Modify /vp9/encoder/vp9_encodeframe.c

  
   Modify /vp9/encoder/x86/vp9_dct32x32_sse2.c

  
   Add /vp9/encoder/x86/vp9_dct_impl_sse2.c

  
   Modify /vp9/encoder/x86/vp9_dct_mmx.asm

  
   Modify /vp9/encoder/x86/vp9_dct_sse2.c

  
   Add /vp9/encoder/x86/vp9_dct_sse2.h

  
   Modify /vp9/vp9cx.mk

  
  
  Added high bitdepth sse2 transform functions

  Also removes some spurious changes in common/vp9_blockd.h which
  was introduced by a rebase issue between nextgen and master branches.

  Change-Id : If359f0e9a71bca9c2ba685a87a355873536bb282
  (cherry picked from commit 005d80cd05269a299cd2f7ddbc3d4d8b791aebba)
  (cherry picked from commit 08d2f548007fd8d6fd41da8ef7fdb488b6485af3)
  (cherry picked from commit 4230c2306c194c058f56433a5275aa02a2e71d56)