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• FFmpeg av_read_frame returns a size but no data ?

  11 décembre 2013, par tommed

  I have written some C code to access ffmpeg and wrapped it in a C++/CLI (.NET managed) class. The program fetches a live video stream and extracts frames and converts them to PNG files.

  Unfortunately the images that are saved to disk are always black (opening them in Notepad++ shows that they are full of nulls).

  I am using the assemblies aformat/codec-55.dll and the development headers and libs for compilation from ffmpeg-20131120-git-e502783-win64-dev. The whole project is compiled using Managed C++ (Cpp/cli) .NET 4.0 for 64-bit.

  After some investigation the problem appears to be that av_read_frame fills the AVPacket->size value correctly, but the AVPAcket->data is always null. When the frame is finished (got==1) then the data for the AVFrame is just a matrix of nulls. :(

  Here is the code :
  Example code (sorry, but it didnt paste well into SO)

  I think the problem is at line 34 when the packet is returned like so :
  

  Please, how can I get this to work ? What have I done wrong ?

• C++/CLI FFmpeg av_read_frame returns a size but no data ?

  26 novembre 2013, par tommed

  I have written some C code to access ffmpeg and wrapped it in a C++/CLI (.NET managed) class. The program fetches a live video stream and extracts frames and converts them to PNG files.

  Unfortunately the images that are saved to disk are always black (opening them in Notepad++ shows that they are full of nulls).

  I am using the assemblies aformat/codec-55.dll and the development headers and libs for compilation from ffmpeg-20131120-git-e502783-win64-dev. The whole project is compiled using Managed C++ (Cpp/cli) .NET 4.0 for 64-bit.

  After some investigation the problem appears to be that av_read_frame fills the AVPacket->size value correctly, but the AVPAcket->data is always null. When the frame is finished (got==1) then the data for the AVFrame is just a matrix of nulls. :(

  Here is the code :
  Example code (sorry, but it didnt paste well into SO)

  I think the problem is at line 34 when the packet is returned like so :
  

  Please, how can I get this to work ? What have I done wrong ?

• How do I change audio language using ffmpeg in video files contaning two or more audio tracks

  19 mai 2020, par warezsoftwarez

  I am transcoding video files, that contain 2 audio tracks - Polish and English. Unfortunately my transcoder messes somehow with metadata, and at the output, when I'm checking video file using MediaInfo, i see that both audio tracks are described as English. I'd like to change description of 1st audio track to Polish, so accordingly to ffmpeg documentation :

  



  To set the language of the first audio stream:
ffmpeg -i INPUT -metadata:s:a:0 language=eng OUTPUT


  



  Unfortunately, running command :

  



  ffmpeg -i INPUTPATH -metadata:s:a:0 language=pol OUTPUTPATH


  



  to overwrite input file resulted in saving file thats size is 63KB but it is described as Polish audio (no second audio track - English somehow was deleted)

  



  When I used this command, to save output file as another file, to avoid overwriting if something misses (which is current situation), but using parameter -metadata:s:a:4 because I thought that maybe I'm reading metadata from ffmpeg incorrectly, it resulted in saving output file as 800Mb with only English (no Polish track).

  



  I don't know what should I change in this command to run as I want it to - just changing metadata of first audio track language to Polish.

  



  Here is full ffmpeg output :

  



  C:\Users\user>ffmpeg -i F:\Path\33244813_6000_1_trailer.mp4 -metadata:s:a:4 language=pol F:\Path\testtest.mp4
ffmpeg version N-91931-gb69ea742ab Copyright (c) 2000-2018 the FFmpeg developers
  built with gcc 8.2.1 (GCC) 20180813
  configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-fontconfig --enable-gnutls --enable-iconv --enabl
e-libass --enable-libbluray --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amr
wb --enable-libopenjpeg --enable-libopus --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libtheora --enab
le-libtwolame --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --
enable-libzimg --enable-lzma --enable-zlib --enable-gmp --enable-libvidstab --enable-libvorbis --enable-libvo-amrwbenc -
-enable-libmysofa --enable-libspeex --enable-libxvid --enable-libaom --enable-libmfx --enable-amf --enable-ffnvcodec --e
nable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec --enable-dxva2 --enable-avisynth
  libavutil      56. 19.101 / 56. 19.101
  libavcodec     58. 30.100 / 58. 30.100
  libavformat    58. 18.100 / 58. 18.100
  libavdevice    58.  4.103 / 58.  4.103
  libavfilter     7. 29.100 /  7. 29.100
  libswscale      5.  2.100 /  5.  2.100
  libswresample   3.  2.100 /  3.  2.100
  libpostproc    55.  2.100 / 55.  2.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'F:\Path\33244813_6000_1_trailer.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 1
    compatible_brands: isom
    creation_time   : 2020-04-22T16:18:04.000000Z
  Duration: 00:40:39.12, start: 0.000000, bitrate: 8848 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 1920x1080 [SAR 1:1 DAR 16:9], Closed C
aptions, 5068 kb/s, 25 fps, 25 tbr, 120k tbn, 50 tbc (default)
    Metadata:
      creation_time   : 2020-04-22T16:18:04.000000Z
      handler_name    : Video
    Stream #0:1(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 1920x1080 [SAR 1:1 DAR 16:9], Closed C
aptions, 1857 kb/s, 25 fps, 25 tbr, 120k tbn, 50 tbc (default)
    Metadata:
      creation_time   : 2020-04-22T16:18:04.000000Z
      handler_name    : Video
    Stream #0:2(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 1280x720 [SAR 1:1 DAR 16:9], Closed Ca
ptions, 902 kb/s, 25 fps, 25 tbr, 120k tbn, 50 tbc (default)
    Metadata:
      creation_time   : 2020-04-22T16:18:04.000000Z
      handler_name    : Video
    Stream #0:3(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 640x480 [SAR 4:3 DAR 16:9], Closed Cap
tions, 628 kb/s, 25 fps, 25 tbr, 120k tbn, 50 tbc (default)
    Metadata:
      creation_time   : 2020-04-22T16:18:04.000000Z
      handler_name    : Video
    Stream #0:4(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 125 kb/s (default)
    Metadata:
      creation_time   : 2020-04-22T16:18:04.000000Z
      handler_name    : Sound
    Stream #0:5(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, 5.1, fltp, 253 kb/s (default)
    Metadata:
      creation_time   : 2020-04-22T16:18:04.000000Z
      handler_name    : Sound
Stream mapping:
  Stream #0:0 -> #0:0 (h264 (native) -> h264 (libx264))
  Stream #0:5 -> #0:1 (aac (native) -> aac (native))
Press [q] to stop, [?] for help
[libx264 @ 00000012bef91f80] using SAR=1/1
[libx264 @ 00000012bef91f80] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
[libx264 @ 00000012bef91f80] profile High, level 4.0, 4:2:0, 8-bit
[libx264 @ 00000012bef91f80] 264 - core 157 r2932 303c484 - H.264/MPEG-4 AVC codec - Copyleft 2003-2018 - http://www.vid
eolan.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=34 looka
head_threads=5 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_lookah
ead=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 'F:\Path\testtest.mp4'
:
  Metadata:
    major_brand     : isom
    minor_version   : 1
    compatible_brands: isom
    encoder         : Lavf58.18.100
    Stream #0:0(und): Video: h264 (libx264) (avc1 / 0x31637661), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], q=-1--1, 25 fps,
 12800 tbn, 25 tbc (default)
    Metadata:
      creation_time   : 2020-04-22T16:18:04.000000Z
      handler_name    : Video
      encoder         : Lavc58.30.100 libx264
    Side data:
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
    Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, 5.1, fltp, 341 kb/s (default)
    Metadata:
      creation_time   : 2020-04-22T16:18:04.000000Z
      handler_name    : Sound
      encoder         : Lavc58.30.100 aac
frame=60981 fps= 84 q=-1.0 Lsize=  816313kB time=00:40:39.12 bitrate=2741.7kbits/s dup=3 drop=0 speed=3.36x
video:713292kB audio:101322kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.208512%
[libx264 @ 00000012bef91f80] frame I:769   Avg QP:16.36  size: 46713
[libx264 @ 00000012bef91f80] frame P:37125 Avg QP:19.81  size: 15059
[libx264 @ 00000012bef91f80] frame B:23087 Avg QP:21.11  size:  5866
[libx264 @ 00000012bef91f80] consecutive B-frames: 40.4% 24.0% 10.2% 25.5%
[libx264 @ 00000012bef91f80] mb I  I16..4: 40.3% 58.0%  1.7%
[libx264 @ 00000012bef91f80] mb P  I16..4:  6.2% 12.5%  0.1%  P16..4: 29.8%  3.7%  2.7%  0.0%  0.0%    skip:45.0%
[libx264 @ 00000012bef91f80] mb B  I16..4:  1.0%  1.7%  0.0%  B16..8: 27.9%  1.1%  0.1%  direct: 2.0%  skip:66.2%  L0:49
.4% L1:49.3% BI: 1.3%
[libx264 @ 00000012bef91f80] 8x8 transform intra:65.3% inter:95.1%
[libx264 @ 00000012bef91f80] coded y,uvDC,uvAC intra: 24.7% 39.7% 3.2% inter: 7.0% 14.6% 0.0%
[libx264 @ 00000012bef91f80] i16 v,h,dc,p: 34% 26% 13% 28%
[libx264 @ 00000012bef91f80] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 25% 15% 41%  3%  3%  4%  3%  3%  2%
[libx264 @ 00000012bef91f80] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 32% 25% 20%  3%  6%  5%  4%  3%  2%
[libx264 @ 00000012bef91f80] i8c dc,h,v,p: 58% 19% 20%  3%
[libx264 @ 00000012bef91f80] Weighted P-Frames: Y:0.1% UV:0.0%
[libx264 @ 00000012bef91f80] ref P L0: 72.2%  6.3% 15.8%  5.7%  0.0%
[libx264 @ 00000012bef91f80] ref B L0: 86.6% 11.5%  1.9%
[libx264 @ 00000012bef91f80] ref B L1: 97.6%  2.4%
[libx264 @ 00000012bef91f80] kb/s:2395.53
[aac @ 00000012bef93b00] Qavg: 471.415