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• ffmpeg poor YUV to RGB in sws_scale() (was : ffmpeg blocky chroma decoding)

  12 septembre 2017, par noiseshaper

  I’m using ffmpeg-3.2.4-win32, static and dev versions from zeranoe page, to decode some h264 mp4 videos I have created with x264 encoder. The videos have lots of static zones, 2d videogame type.

  When I decode their frames using either ffmpeg.exe or avcodec_decode_video2() API function, I get poor chroma resolution, blocky and quite visible in the static zones of the video (edit : avcodec_decode_video2() returns correct YUV, the problem is the YUV->RGB conversion, see my own answer below).

  With ffmpeg.exe I get poor chroma only if I output the frames to png, but if I output them to jpg, chroma seems much better (edit : this is due to poor YUV to RGB conversion of ffmpeg’s sws_scale()).

  Here is an example of the same frame obtained from a mp4 video created with a static image, the output frame is zoomed in to clearly see the effect.

  https://drive.google.com/file/d/0B5KI1D-N1kHpV3lGaERJRjNkcms/view

  1 : Original frame before compressing.

  2 : YUV 4:2:0 conversion before compressing

  3 : Video output from MPC HC + LAV decoder. This is YUV decoded output.

  4 : Video frames decoded with ffmpeg.exe to jpeg, quality is mostly ok, just some jpeg macroblocking is visible.

  5 : Video frames decoded with ffmpeg.exe to png, very blocky chroma. This is RGB output, using avcodec_decode_video2() and sws_scale() conversion to RGB produces the same blocky chroma.

  ---

  The command lines for decoding the frames to jpg and png are these :

  ffmpeg -i testcase.mp4 -vframes 5 -qscale:v 2 output%03d.jpg

  ffmpeg -i testcase.mp4 -vframes 5 output%03d.png

  You can download mp4 and bat files that showcase the effect here :

  https://drive.google.com/drive/folders/0B5KI1D-N1kHpcUdGd2IyM2pXMTg

  ---

  I have tried with ffmpeg 3.2, but same thing happens.

• ffmpeg blocky chroma decoding

  12 septembre 2017, par noiseshaper

  I’m using ffmpeg-3.2.4-win32, static and dev versions from zeranoe page, to decode some h264 mp4 videos I have created with x264 encoder. The videos have lots of static zones, 2d videogame type.

  When I decode their frames using either ffmpeg.exe or avcodec_decode_video2() API function, I get poor chroma resolution, blocky and quite visible in the static zones of the video (edit : avcodec_decode_video2() returns correct YUV, the problem is the YUV->RGB conversion, see my own answer).

  Strangely, with ffmpeg.exe I get poor chroma only if I output the frames to png, but if I output them to jpg, chroma seems much better.

  The videos are 30 fps full hd videos created from static images or from Lagarith RGB captures, converted to YUV with Rec.709 colormatrix and then input to x264.exe using crf 20 and baseline profile. Using high profile makes no difference in my tests (edit : irrelevant, since the problem is in the YUV->RGB conversion).

  If I play a mp4 video with ffplay.exe or MPC HC + LAV decoder, the chroma is good, nearly equal to the uncompressed YUV 4:2:0 version.

  Here is an example of the same frame obtained from a mp4 video created with a static image, the output frame is zoomed in to clearly see the effect.

  https://drive.google.com/file/d/0B5KI1D-N1kHpV3lGaERJRjNkcms/view

  1 : Original frame before compressing.

  2 : YUV 4:2:0 conversion before compressing

  3 : Video output from MPC HC + LAV decoder. ffplay output looks the same.

  4 : Video frames decoded with ffmpeg.exe to jpeg, some jpeg macroblocking is visible.

  5 : Video frames decoded with ffmpeg.exe to png, very blocky chroma. Using avcodec_decode_video2() function, the YUV output or its conversion to RGB produces the same blocky chroma.

  ---

  The command lines for decoding the frames to jpg and png are these :

  ffmpeg -i testcase.mp4 -vf colormatrix=bt709:bt601 -vframes 5 -qscale:v 2 output%03d.jpg

  ffmpeg -i testcase.mp4 -vf colormatrix=bt709:bt601 -vframes 5 output%03d.png

  You can download mp4 and bat files that showcase the effect here :

  https://drive.google.com/drive/folders/0B5KI1D-N1kHpcUdGd2IyM2pXMTg

  ---

  I have tried with ffmpeg 3.2, but same thing happens.

• ffmpeg - whatsapp : video format not supported

  10 septembre 2023, par Santhosh

  I have two videos (.mp4) files. One uploads to whatsapp and another does not.

  



  Using ffmpeg I checked their properties :

  



  a) Properties of video which uploads :

  



    Duration: 00:00:56.45, start: 0.148000, bitrate: 1404 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1080x1080, 1359 kb/s, 23.98 fps, 23.98 tbr, 90k tbn, 47.95 tbc (default)
    Metadata:
      handler_name    : VideoHandler
    Stream #0:1(eng): Audio: aac (HE-AACv2) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 47 kb/s (default)
    Metadata:
      handler_name    : SoundHandler
At least one output file must be specified


  



  b) video which does not upload to whatsapp (because its says format not supported)

  



    Duration: 00:00:56.10, start: 0.000000, bitrate: 543 kb/s
    Stream #0:0: Video: h264 (High) (H264 / 0x34363248), yuv420p, 1080x1080 [SAR 1:1 DAR 1:1], 464 kb/s, 23.98 fps, 23.98 tbr, 23.98 tbn, 47.95 tbc
    Stream #0:1: Audio: aac (LC) ([255][0][0][0] / 0x00FF), 48000 Hz, stereo, fltp, 56 kb/s


  



  The difference in video I noticed :

  



  (avc1 / 0x31637661) vs (H264 / 0x34363248)

  



  1359 kb/s vs 464 kb/s

  



  90k tbn vs 23.98 tbn

  



  What can be the reason ?

  



  Also the second video is not being played in Android.

  



  The link for the video is https://drive.google.com/open?id=0B4UM6vTHw4pyMExQQ1lxZGp0N2c