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• decode raw buffer with ffmpeg av_codec_video_2

  19 décembre 2015, par will.I4M

  I’m trying to write a decoder for a webrtc app in C. I receive a RTP stream, I parse every packet, reorder them, and put the payload in a AVPacket, as described here (FFmpeg decode raw buffer with avcodec_decode_video2).
  The reordering part is not described in this link but I’m pretty sure this part is OK.

  The question is, I dont know how to give the decoder information about resolution, pix_fmt etc. Do I need to create an AVstream* and fill it with all information I took from rtp header ?

  Do someone have a piece of running code that decode a VP8 packet depacketized without the use of rtp_dec etc.?

  In this link, no more information seems to be sent to the decoder, is it able to decode without knowing resolution and without any header ?

• fate : Add test for colorkey

  21 janvier 2016, par Michael Niedermayer

  fate : Add test for colorkey
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] tests/fate/ffmpeg.mak
  • [DH] tests/filtergraphs/colorkey
  • [DH] tests/ref/fate/ffmpeg-filter_colorkey

• Prevent ffmpeg from changing the intensity of colors while downscaling the resolution of the video

  29 août 2022, par dravit

  I have a use case where I need to downscale a 716x1280 mp4 video to 358x640 (half of the original). Command that I used is

  


  ffmpeg -i ./input.mp4 -vf "scale=640:640:force_original_aspect_ratio=decrease,pad=ceil(iw/2)*2:ceil(ih/2)*2" ./output.mp4


  


  Out of 10 sample videos, 2 of the them suffered impact on colors. Below I have attached a comparison from the one which was impacted the most.

  


  

  


  NOTE : The one on the right is a frame from the original video and the frame on the left is the one from the processed (down scaled) video. Notice the colors red and green in the image (even the skin color and hair color were changed).

  


  What I am looking for is

  


  

  • Is there any way I can prevent changes like these happening ? Probably some flag on saturation, brightness, contrast or any other parameter.

  


  • I am assuming that ffmpeg uses some default settings while downscaling a video. What made ffmpeg change colors only for these two videos ? If it made similar changes for the rest of the videos as well, how to predict this behaviour before hand ?

  


  


  EDIT :

  


  What I already have Tried ?

  


  

  • -crf with values 0 and 18.

  


  • -preset veryslow as mentioned here

  


  


  None helped

  


  Mediainfo input V/S output

  


  





  


  


  


  


  


  



  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  param	input	output
  color range	Limited	NA (attribute not in description)
  color primaries	BT.2020	NA (attribute not in description)
  transfer characteristics	HLG	NA (attribute not in description)
  matrix coefficients	BT.2020 non-constant	NA (attribute not in description)
  bit deapth	8	8

  


  


  Logs of the ffmpeg command

  


  ffmpeg -i ./input.mp4 -vf "scale=640:640:force_original_aspect_ratio=decrease,pad=ceil(iw/2)*2:ceil(ih/2)*2" -movflags +faststart ./output.mp4
ffmpeg version 4.3.1 Copyright (c) 2000-2020 the FFmpeg developers
  built with Apple clang version 12.0.0 (clang-1200.0.32.28)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/4.3.1_9 --enable-shared --enable-pthreads --enable-version3 --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libdav1d --enable-libmp3lame --enable-libopus --enable-librav1e --enable-librubberband --enable-libsnappy --enable-libsrt --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librtmp --enable-libspeex --enable-libsoxr --enable-videotoolbox --enable-libzmq --enable-libzimg --disable-libjack --disable-indev=jack
  libavutil      56. 51.100 / 56. 51.100
  libavcodec     58. 91.100 / 58. 91.100
  libavformat    58. 45.100 / 58. 45.100
  libavdevice    58. 10.100 / 58. 10.100
  libavfilter     7. 85.100 /  7. 85.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  7.100 /  5.  7.100
  libswresample   3.  7.100 /  3.  7.100
  libpostproc    55.  7.100 / 55.  7.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from './input.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.45.100
  Duration: 00:00:30.05, start: 0.000000, bitrate: 10366 kb/s
    Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, bt2020nc/bt2020/arib-std-b67), 716x1280, 10116 kb/s, 30 fps, 30 tbr, 19200 tbn, 38400 tbc (default)
    Metadata:
      handler_name    : Core Media Video
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 245 kb/s (default)
    Metadata:
      handler_name    : Core Media Audio
Stream mapping:
  Stream #0:0 -> #0:0 (h264 (native) -> h264 (libx264))
  Stream #0:1 -> #0:1 (aac (native) -> aac (native))
Press [q] to stop, [?] for help
[libx264 @ 0x7faab4808800] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
[libx264 @ 0x7faab4808800] profile High, level 3.0, 4:2:0, 8-bit
[libx264 @ 0x7faab4808800] 264 - core 161 r3027 4121277 - H.264/MPEG-4 AVC codec - Copyleft 2003-2020 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=12 lookahead_threads=2 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
Output #0, mp4, to './output.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.45.100
    Stream #0:0(und): Video: h264 (libx264) (avc1 / 0x31637661), yuv420p, 358x640, q=-1--1, 30 fps, 15360 tbn, 30 tbc (default)
    Metadata:
      handler_name    : Core Media Video
      encoder         : Lavc58.91.100 libx264
    Side data:
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: N/A
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 128 kb/s (default)
    Metadata:
      handler_name    : Core Media Audio
      encoder         : Lavc58.91.100 aac
[mp4 @ 0x7faab5808800] Starting second pass: moving the moov atom to the beginning of the file
frame=  901 fps=210 q=-1.0 Lsize=    3438kB time=00:00:30.02 bitrate= 938.0kbits/s speed=7.01x
video:2933kB audio:472kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.974633%
[libx264 @ 0x7faab4808800] frame I:6     Avg QP:22.60  size: 20769
[libx264 @ 0x7faab4808800] frame P:228   Avg QP:24.84  size:  7657
[libx264 @ 0x7faab4808800] frame B:667   Avg QP:27.59  size:  1697
[libx264 @ 0x7faab4808800] consecutive B-frames:  0.9%  0.9%  1.0% 97.2%
[libx264 @ 0x7faab4808800] mb I  I16..4:  9.5% 64.6% 26.0%
[libx264 @ 0x7faab4808800] mb P  I16..4:  2.5% 12.2%  2.5%  P16..4: 37.2% 20.6% 11.2%  0.0%  0.0%    skip:13.7%
[libx264 @ 0x7faab4808800] mb B  I16..4:  0.4%  2.1%  0.2%  B16..8: 42.2%  7.1%  1.2%  direct: 1.8%  skip:44.9%  L0:39.4% L1:52.8% BI: 7.8%
[libx264 @ 0x7faab4808800] 8x8 transform intra:72.2% inter:74.2%
[libx264 @ 0x7faab4808800] coded y,uvDC,uvAC intra: 61.8% 67.2% 20.2% inter: 16.7% 13.9% 1.3%
[libx264 @ 0x7faab4808800] i16 v,h,dc,p: 24% 19%  7% 50%
[libx264 @ 0x7faab4808800] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 21% 16% 15%  6%  9% 11%  7% 10%  6%
[libx264 @ 0x7faab4808800] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 25% 16% 13%  7%  9% 10%  7%  9%  4%
[libx264 @ 0x7faab4808800] i8c dc,h,v,p: 53% 16% 26%  5%
[libx264 @ 0x7faab4808800] Weighted P-Frames: Y:3.9% UV:1.8%
[libx264 @ 0x7faab4808800] ref P L0: 57.8% 19.5% 14.8%  7.8%  0.1%
[libx264 @ 0x7faab4808800] ref B L0: 90.7%  7.2%  2.1%
[libx264 @ 0x7faab4808800] ref B L1: 95.3%  4.7%
[libx264 @ 0x7faab4808800] kb/s:799.80
[aac @ 0x7faab2036a00] Qavg: 189.523