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• AAC decoding with FFmpeg and Audio Toolbox decoder on the Mac not working

  20 juin 2017, par MrBigPixel

  I’m connecting to an mp4 RTSP stream with AAC audio. Connecting to it via command line ffmpeg and specifying "aac_at" for the decoder does playback audio correctly.

  However in my code when connecting to the same stream using avcodec_find_decoder_by_name("aac_at")
  the audio toolbox decoder produces white noise.

  To verify the correctness of the code by just replacing that line with
  avcodec_find_decoder_by_name("aac")
  the decoder does produce correct audio.

  Has anybody else experienced anything like this when using the ffmpeg libs and the audio toolbox AAC decoder on the Mac ?

• Cannot find yasm even though I have installed it

  20 juillet 2017, par zhen lee

  I got a strange problem. I tried to install x264. When run sudo ./configure —enable-shared,
  it gave :

  Found no assembler
  Minimum version is yasm-0.7.0
  If you really want to compile without asm, configure with —disable-asm.

  But I already installed yasm-0.7.0 ,to prove that ,i run yasm —version,it gave :

  *yasm 0.7.0.2066
  Compiled on May 8 2012.
  Copyright (c) 2001-2008 Peter Johnson and other Yasm developers.
  Run yasm —license for licensing overview and summary.*

  I install yasm to /usr/local/yasm,
  Why can it not find yasm ?

• What is wrong with the following ffmpeg command

  9 juin 2017, par Brad

  What is wrong with the following ffmpeg command ? Originally this had -sameq instead of the -qscale:a 0

  Command :

  ffmpeg -loglevel debug -threads 4 -i sample-in.mpg -ss 00:00:01 -t 00:00:05 -f image2 -y sample-frames/frame%d.png -acodec copy -qscale:a 0  -y sample.mp3

  ---

  Output

  ffmpeg version 1.2.1 Copyright (c) 2000-2013 the FFmpeg developers
  
    built on Jul  9 2013 04:36:42 with Apple clang version 4.1 (tags/Apple/clang-421.11.66) (based on LLVM 3.1svn)
  
    configuration: --prefix=/usr/local/Cellar/ffmpeg/1.2.1 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-nonfree --enable-hardcoded-tables --enable-avresample --enable-vda --cc=cc --host-cflags= --host-ldflags= --enable-libx264 --enable-libfaac --enable-libmp3lame --enable-libxvid --enable-ffplay
  
    libavutil      52. 18.100 / 52. 18.100
  
    libavcodec     54. 92.100 / 54. 92.100
  
    libavformat    54. 63.104 / 54. 63.104
  
    libavdevice    54.  3.103 / 54.  3.103
  
    libavfilter     3. 42.103 /  3. 42.103
  
    libswscale      2.  2.100 /  2.  2.100
  
    libswresample   0. 17.102 /  0. 17.102
  
    libpostproc    52.  2.100 / 52.  2.100
  
  
  
  Splitting the commandline.
  
  Reading option '-loglevel' ... matched as option 'loglevel' (set libav* logging level) with argument 'debug'.
  
  Reading option '-threads' ... matched as AVOption 'threads' with argument '4'.
  
  Reading option '-i' ... matched as input file with argument 'sample-in.mpg'.
  
  Reading option '-ss' ... matched as option 'ss' (set the start time offset) with argument '00:00:01'.
  
  Reading option '-t' ... matched as option 't' (record or transcode "duration" seconds of audio/video) with argument '00:00:05'.
  
  Reading option '-f' ... matched as option 'f' (force format) with argument 'image2'.
  
  Reading option '-y' ... matched as option 'y' (overwrite output files) with argument '1'.
  
  Reading option 'sample-frames/frame%d.png' ... matched as output file.
  
  Reading option '-acodec' ... matched as option 'acodec' (force audio codec ('copy' to copy stream)) with argument 'copy'.
  
  Reading option '-qscale:a' ... matched as option 'qscale' (use fixed quality scale (VBR)) with argument '0'.
  
  Reading option '-y' ... matched as option 'y' (overwrite output files) with argument '1'.
  
  Reading option 'sample.mp3' ... matched as output file.
  
  Finished splitting the commandline.
  
  Parsing a group of options: global .
  
  Applying option loglevel (set libav* logging level) with argument debug.
  
  Applying option y (overwrite output files) with argument 1.
  
      Last message repeated 1 times
  
  Successfully parsed a group of options.
  
  Parsing a group of options: input file sample-in.mpg.
  
  Successfully parsed a group of options.
  
  Opening an input file: sample-in.mpg.
  
  [mpeg @ 0x7ffb4a80f200] Format mpeg probed with size=16384 and score=52
  
  [mpeg @ 0x7ffb4a80f200] File position before avformat_find_stream_info() is 0
  
  [mpeg @ 0x7ffb4a80f200] probing stream 0 pp:2500
  
  [mpeg @ 0x7ffb4a80f200] Probe with size=2002, packets=1 detected mpegvideo with score=25
  
  [mpeg @ 0x7ffb4a80f200] probing stream 0 pp:2499
  
  [mpeg @ 0x7ffb4a80f200] Probe with size=4043, packets=2 detected mpegvideo with score=25
  
  [mpeg @ 0x7ffb4a80f200] probing stream 0 pp:2498
  
  [mpeg @ 0x7ffb4a80f200] Probe with size=6084, packets=3 detected mpegvideo with score=25
  
  [mpeg @ 0x7ffb4a80f200] probing stream 0 pp:2497
  
  [mpeg @ 0x7ffb4a80f200] probing stream 0 pp:2496
  
  [mpeg @ 0x7ffb4a80f200] Probe with size=10166, packets=5 detected mpegvideo with score=25
  
  [mpeg @ 0x7ffb4a80f200] probing stream 0 pp:2495
  
  [mpeg @ 0x7ffb4a80f200] probing stream 0 pp:2494
  
  [mpeg @ 0x7ffb4a80f200] probing stream 0 pp:2493
  
  [mpeg @ 0x7ffb4a80f200] probing stream 0 pp:2492
  
  [mpeg @ 0x7ffb4a80f200] Probe with size=18330, packets=9 detected mpegvideo with score=25
  
  [mpeg @ 0x7ffb4a80f200] probing stream 0 pp:2491
  
  [mpeg @ 0x7ffb4a80f200] probing stream 0 pp:2490
  
  [mpeg @ 0x7ffb4a80f200] probing stream 0 pp:2489
  
  [mpeg @ 0x7ffb4a80f200] probing stream 0 pp:2488
  
  [mpeg @ 0x7ffb4a80f200] probing stream 0 pp:2487
  
  [mpeg @ 0x7ffb4a80f200] probing stream 0 pp:2486
  
  [mpeg @ 0x7ffb4a80f200] probing stream 0 pp:2485
  
  [mpeg @ 0x7ffb4a80f200] probing stream 0 pp:2484
  
  [mpeg @ 0x7ffb4a80f200] Probe with size=34658, packets=17 detected mpegvideo with score=25
  
  [mpeg @ 0x7ffb4a80f200] probing stream 0 pp:2483
  
  [mpeg @ 0x7ffb4a80f200] probing stream 0 pp:2482
  
  [mpeg @ 0x7ffb4a80f200] probing stream 0 pp:2481
  
  [mpeg @ 0x7ffb4a80f200] probing stream 0 pp:2480
  
  [mpeg @ 0x7ffb4a80f200] probing stream 0 pp:2479
  
  [mpeg @ 0x7ffb4a80f200] probing stream 0 pp:2478
  
  [mpeg @ 0x7ffb4a80f200] probing stream 0 pp:2477
  
  [mpeg @ 0x7ffb4a80f200] probing stream 0 pp:2476
  
  [mpeg @ 0x7ffb4a80f200] probing stream 0 pp:2475
  
  [mpeg @ 0x7ffb4a80f200] probing stream 0 pp:2474
  
  [mpeg @ 0x7ffb4a80f200] probing stream 0 pp:2473
  
  [mpeg @ 0x7ffb4a80f200] probing stream 0 pp:2472
  
  [mpeg @ 0x7ffb4a80f200] probing stream 0 pp:2471
  
  [mpeg @ 0x7ffb4a80f200] probing stream 0 pp:2470
  
  [mpeg @ 0x7ffb4a80f200] probing stream 0 pp:2469
  
  [mpeg @ 0x7ffb4a80f200] probing stream 0 pp:2468
  
  [mpeg @ 0x7ffb4a80f200] Probe with size=67266, packets=33 detected mpegvideo with score=51
  
  [mpeg @ 0x7ffb4a80f200] probed stream 0
  
  [mpeg @ 0x7ffb4a80f200] first_dts 86997 not matching first dts 93003 in the queue
  
      Last message repeated 3 times
  
  [mpeg @ 0x7ffb4a80f200] first_dts 86997 not matching first dts 108018 in the queue
  
      Last message repeated 3 times
  
  [mpeg @ 0x7ffb4a80f200] first_dts 90000 not matching first dts 111600 in the queue
  
      Last message repeated 9 times
  
  [mpeg @ 0x7ffb4a80f200] first_dts 90000 not matching first dts 135360 in the queue
  
      Last message repeated 8 times
  
  [mpeg @ 0x7ffb4a80f200] first_dts 90000 not matching first dts 156960 in the queue
  
      Last message repeated 9 times
  
  [mpeg @ 0x7ffb4a80f200] first_dts 90000 not matching first dts 180720 in the queue
  
      Last message repeated 8 times
  
  [mpeg @ 0x7ffb4a80f200] first_dts 90000 not matching first dts 202320 in the queue
  
      Last message repeated 9 times
  
  [mpeg @ 0x7ffb4a80f200] first_dts 90000 not matching first dts 226080 in the queue
  
      Last message repeated 8 times
  
  [mpeg @ 0x7ffb4a80f200] first_dts 90000 not matching first dts 247680 in the queue
  
      Last message repeated 9 times
  
  [mpeg @ 0x7ffb4a80f200] first_dts 90000 not matching first dts 271440 in the queue
  
      Last message repeated 9 times
  
  [mpeg @ 0x7ffb4a80f200] first_dts 90000 not matching first dts 295200 in the queue
  
      Last message repeated 8 times
  
  [mpeg @ 0x7ffb4a80f200] first_dts 90000 not matching first dts 316800 in the queue
  
      Last message repeated 9 times
  
  [mpeg @ 0x7ffb4a80f200] first_dts 90000 not matching first dts 340560 in the queue
  
      Last message repeated 8 times
  
  [mpeg @ 0x7ffb4a80f200] first_dts 90000 not matching first dts 362160 in the queue
  
      Last message repeated 9 times
  
  [mpeg @ 0x7ffb4a80f200] first_dts 90000 not matching first dts 385920 in the queue
  
      Last message repeated 8 times
  
  [mpeg @ 0x7ffb4a80f200] first_dts 90000 not matching first dts 407520 in the queue
  
      Last message repeated 9 times
  
  [mpeg @ 0x7ffb4a80f200] first_dts 90000 not matching first dts 431280 in the queue
  
      Last message repeated 8 times
  
  [mpeg @ 0x7ffb4a80f200] first_dts 90000 not matching first dts 452880 in the queue
  
      Last message repeated 9 times
  
  [mpeg @ 0x7ffb4a80f200] first_dts 90000 not matching first dts 476640 in the queue
  
      Last message repeated 8 times
  
  [mpeg @ 0x7ffb4a80f200] first_dts 90000 not matching first dts 498240 in the queue
  
      Last message repeated 9 times
  
  [mpeg @ 0x7ffb4a80f200] first_dts 90000 not matching first dts 522000 in the queue
  
      Last message repeated 9 times
  
  [mpeg @ 0x7ffb4a80f200] max_analyze_duration 5000000 reached at 5005000 microseconds
  
  [mpeg @ 0x7ffb4a80f200] File position after avformat_find_stream_info() is 0
  
  Input #0, mpeg, from 'sample-in.mpg':
  
    Duration: 00:00:05.97, start: 1.000000, bitrate: 6827 kb/s
  
      Stream #0:0[0x1e0], 152, 1/90000: Video: mpeg1video, yuv420p, 704x480 [SAR 200:219 DAR 880:657], 1001/30000, 104857 kb/s, 29.97 fps, 29.97 tbr, 90k tbn, 29.97 tbc
  
      Stream #0:1[0x1c0], 211, 1/90000: Audio: mp2, 48000 Hz, stereo, s16p, 64 kb/s
  
  Successfully opened the file.
  
  Parsing a group of options: output file sample-frames/frame%d.png.
  
  Applying option ss (set the start time offset) with argument 00:00:01.
  
  Applying option t (record or transcode "duration" seconds of audio/video) with argument 00:00:05.
  
  Applying option f (force format) with argument image2.
  
  Successfully parsed a group of options.
  
  Opening an output file: sample-frames/frame%d.png.
  
  Successfully opened the file.
  
  Parsing a group of options: output file sample.mp3.
  
  Applying option acodec (force audio codec ('copy' to copy stream)) with argument copy.
  
  Applying option qscale:a (use fixed quality scale (VBR)) with argument 0.
  
  Successfully parsed a group of options.
  
  Opening an output file: sample.mp3.
  
  Successfully opened the file.
  
  [buffer @ 0x7ffb4a411e40] Setting entry with key 'video_size' to value '704x480'
  
  [buffer @ 0x7ffb4a411e40] Setting entry with key 'pix_fmt' to value '0'
  
  [buffer @ 0x7ffb4a411e40] Setting entry with key 'time_base' to value '1/90000'
  
  [buffer @ 0x7ffb4a411e40] Setting entry with key 'pixel_aspect' to value '200/219'
  
  [buffer @ 0x7ffb4a411e40] Setting entry with key 'sws_param' to value 'flags=2'
  
  [buffer @ 0x7ffb4a411e40] Setting entry with key 'frame_rate' to value '30000/1001'
  
  [graph 0 input from stream 0:0 @ 0x7ffb4a411de0] w:704 h:480 pixfmt:yuv420p tb:1/90000 fr:30000/1001 sar:200/219 sws_param:flags=2
  
  [scale @ 0x7ffb4a414800] Setting 'w' to value '0'
  
  [scale @ 0x7ffb4a414800] Setting 'h' to value '0'
  
  [scale @ 0x7ffb4a414800] Setting 'flags' to value '0x4'
  
  [auto-inserted scaler 0 @ 0x7ffb4a414740] w:0 h:0 flags:'0x4' interl:0
  
  [format @ 0x7ffb4a42aa20] auto-inserting filter 'auto-inserted scaler 0' between the filter 'Parsed_null_0' and the filter 'format'
  
  [auto-inserted scaler 0 @ 0x7ffb4a414740] picking rgb24 out of 7 ref:yuv420p alpha:0
  
  [auto-inserted scaler 0 @ 0x7ffb4a414740] w:704 h:480 fmt:yuv420p sar:200/219 -> w:704 h:480 fmt:rgb24 sar:200/219 flags:0x4
  
  [png @ 0x7ffb4a831000] detected 4 logical cores
  
  [mp3 @ 0x7ffb4a831600] Invalid audio stream. Exactly one MP3 audio stream is required.
  
  Output #0, image2, to 'sample-frames/frame%d.png':
  
    Metadata:
  
      encoder         : Lavf54.63.104
  
      Stream #0:0, 0, 1/90000: Video: png, rgb24, 704x480 [SAR 200:219 DAR 880:657], 1001/30000, q=2-31, 200 kb/s, 90k tbn, 29.97 tbc
  
  Output #1, mp3, to 'sample.mp3':
  
    Metadata:
  
      encoder         : Lavf54.63.104
  
      Stream #1:0, 0, 1/90000: Audio: mp2, 48000 Hz, stereo, 64 kb/s
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (mpeg1video -> png)
  
    Stream #0:1 -> #1:0 (copy)
  
  Could not write header for output file #1 (incorrect codec parameters ?): Invalid argument
  
  Statistics: 4542608 bytes read, 2 seeks

  I found the code above from : http://kwlug.org/node/854
  I did a few edits removing the -sameq and replacing it with -qscale:a 0 which probably is wrong.