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• lavc/hevc : Don't parse NAL unit for a dummy buffer

  30 mars 2018, par Haihao Xiang

  lavc/hevc : Don't parse NAL unit for a dummy buffer
  hevc parser mistakenly reports the following message if a dummy buffer
  
  is padded for EOF
     [hevc @ 0x559b63848610] missing picture in access unit
  Signed-off-by : Haihao Xiang <haihao.xiang@intel.com>
  
  Reviewed-by : Steven Liu <lq@chinaffmpeg.org>
  
  Reviewed-by : "Li, Zhong" <zhong.li@intel.com>
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavcodec/hevc_parser.c

• FFmpeg : Invalid NAL unit size after Concat filter

  12 juin 2019, par green_hat

  I am trying to concatenate 3 videos using Concat filter.
  The videos are :

  Video1

  Duration : 00:00:05.34, start : 0.000000, bitrate : 45584 kb/s
  Stream #0:0(eng) : Video : h264 (High) (avc1 / 0x31637661), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], 45653 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)

  Video2

  Duration : 01:12:18.67, start : 0.000000, bitrate : 730 kb/s
  Stream #0:0(und) : Video : h264 (Constrained Baseline) (avc1 / 0x31637661), yuv420p(tv, smpte170m/smpte170m/bt709), 704x352 [SAR 457:704 DAR 457:352], 599 kb/s, 25 fps, 25 tbr, 90k tbn, 50 tbc (default)

  Video3

  Duration : 00:00:10.02, start : 0.000000, bitrate : 25827 kb/s
  Stream #0:0(und) : Video : h264 (High) (avc1 / 0x31637661), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], 25812 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)

  The ffmpeg command that I use is :

  ffmpeg -i video1.mp4 -i video2.mp4 -i video3.mp4 -filter_complex 
  
  "[0:v]scale=1920:1080:force_original_aspect_ratio=1,pad=1920:1080:(ow-iw)/2:(oh-ih)/2,setdar=16/9[v0];
  
  [1:v]scale=1920:1080:force_original_aspect_ratio=1,pad=1920:1080:(ow-iw)/2:(oh-ih)/2,setdar=16/9[v1]; 
  
  [2:v]scale=1920:1080:force_original_aspect_ratio=1,pad=1920:1080:(ow-iw)/2:(oh-ih)/2,setdar=16/9[v2];
  
  [v0][0:a][v1][1:a][v2][2:a] concat=n=3:v=1:a=1[v][a]" 
  
  -map "[v]" -map "[a]" output.mp4
  
  (I have tried also with force_original_aspect_ratio=decrease)

  However I get the following error

  [mov,mp4,m4a,3gp,3g2,mj2 @ 0x55b7422ea700] stream 1, offset 0xbac62: partial files dup=2 drop=0 speed=0.989x
  
  [h264 @ 0x55b742be9a20] Invalid NAL unit size (110724 > 17746).
  
  [h264 @ 0x55b742be9a20] Error splitting the input into NAL units.
  
  video3.mp4: Invalid data found when processing input
  
  video3.mp4: Invalid data found when processing input
  
  Last message repeated 2 times
  
  Error while decoding stream #2:0: Invalid data found when processing input
  
  video3.mp4: Invalid data found when processing input
  
  Last message repeated 1 times

  and the output.mp4 is only video1+video2.

  BUT ! If I use a sample of video2.mp4 (for example the first 10 minutes of it), the ffmpeg command runs successfully till the end, generating the expected output (video1+video2+video3).

  Do you know why do I get this error and how could I cope with it ?

  UPDATE :
  My command works perfectly with a downgraded version of FFmpeg. Maybe there is a bug in the newest one ?

• Why is FFMpeg outputting wrong NAL unit types ? (javascript h264 livestream)

  17 juillet 2018, par Yeti

  I am trying to set up a livestream in the browser using h264 encoding, in which javascript decodes the h264 frames and paints it on a Canvas-element (or using WebGL).

  Both Broadway and Prism implement decoding NAL units of type 1, 5, 7, and 8.

  My current setup is as follows :

  • FFMpeg outputs an MPEG-TS stream with h264 data
  • The stream is piped to netcat which listens on port 8084
  • A websocket server in NodeJS pipes data from port 8084 to clients on 8085
  • The jsmpeg library decodes MPEG-TS into separate NAL units
  • The separate NAL units are decoded by Broadway or Prism which outputs to a canvas

  I am using this FFMpeg command :

  ffmpeg -f v4l2 -i /dev/video0 -r 15 -c:v h264_nvenc -pix_fmt yuv420p -b:v 500k -profile:v baseline -tune zerolatency -f mpegts - | nc -l -p 8084 127.0.0.1

  The problem is that the NAL units I’m getting are of type 9 (or maybe 6 ?), here is the header of one of the NAL units that javascript is receiving, in Base64 and binary formatting :

  echo "AAAAAQnwAAAAAQYBBAAECBCAAAAAAWHg" | base64 -d | xxd -b
  
  00000000: 00000000 00000000 00000000 00000001 00001001 11110000  ......
  
  00000006: 00000000 00000000 00000000 00000001 00000110 00000001  ......
  
  0000000c: 00000100 00000000 00000100 00001000 00010000 10000000  ......
  
  00000012: 00000000 00000000 00000000 00000001 01100001 11100000  ....a.

  Neither Broadway nor Prism supports these NAL unit types. How can I configure FFMpeg to only output NAL units of type 1, 5, 7, and 8 ?

  ---

  EDIT : I have also tried the following command :

  ffmpeg -f v4l2 -i /dev/video0 -r 15 -c:v h264_nvenc -pix_fmt yuv420p \
  
      -b:v 500k -profile:v baseline -tune zerolatency \
  
      -movflags frag_keyframe+empty_moov -g 52 -f mp4 - \
  
      | nc -l -p 8084 127.0.0.1

  Which encodes to mp4, and from there I try to parse NAL units starting with three zero bytes. The lines look all similar to the following :

  echo "AAAACAYBBABOCBCAAAARemHk4f8df1Su" | base64 -d | xxd -b
  
  00000000: 00000000 00000000 00000000 00001000 00000110 00000001  ......
  
  00000006: 00000100 00000000 01001110 00001000 00010000 10000000  ..N...
  
  0000000c: 00000000 00000000 00010001 01111010 01100001 11100100  ...za.
  
  00000012: 11100001 11111111 00011101 01111111 01010100 10101110  ....T.

  That is type 6 (00110 in the 5th byte), still not the desired NAL unit type.

  ---

  UPDATE : The reason it didn’t work for me was a matter of an encoding/decoding issue between chars and bytes in Javascript. I have put the working code on github for others who may want to do a similar thing.

  Concerning the NAL units, it turns out the raw video of FFMpeg output contained type 6 of only a few bytes, followed by type 1 that has the frame data. The type 6 can be discarded. Thanks to the comments and accepted answer for the insight into this.