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• M4a (mp4) audio file encoded with pydub+ffmpeg doesn't play on Android

  6 juillet 2020, par Evelyn

  I have a python script to split up some wav files and export to m4a using pydub. I'm able to get these files to play on several devices, but not on an Android device (using Google Pixel 3). When I try encoding with straight ffmpeg in terminal, that works fine on the Android device.

  


  What is the difference in these two files, and since pydub is using ffmpeg, what do I need to change to make it do exactly the same as the ffmpeg command ?

  


  Not working

  


  from pydub import AudioSegment
>>> audio = AudioSegment.from_wav("input.wav")
>>> slice = audio[1000:3000]
>>> slice.export("pydub_export.m4a", format="mp4", parameters=["-ac", "1", "-c:a", "libfdk_aac", "-profile:a", "aac_he", "-vbr", "2"])


  


  mediainfo output :

  


  General
Complete name                            : pydub_export.m4a
Format                                   : MPEG-4
Format profile                           : Base Media
Codec ID                                 : isom (isom/iso2/mp41)
File size                                : 11.7 KiB
Duration                                 : 2 s 115 ms
Overall bit rate mode                    : Constant
Overall bit rate                         : 45.1 kb/s
Writing application                      : Lavf58.29.100

Audio
ID                                       : 1
Format                                   : AAC LC SBR
Format/Info                              : Advanced Audio Codec Low Complexity with Spectral Band Replication
Commercial name                          : HE-AAC
Format settings                          : NBC
Codec ID                                 : mp4a-40-5
Duration                                 : 2 s 115 ms
Duration_LastFrame                       : -22 ms
Bit rate mode                            : Constant
Bit rate                                 : 41.4 kb/s
Channel(s)                               : 1 channel
Channel layout                           : C
Sampling rate                            : 44.1 kHz
Frame rate                               : 21.533 FPS (2048 SPF)
Compression mode                         : Lossy
Stream size                              : 10.7 KiB (92%)
Default                                  : Yes
Alternate group                          : 1


  


  Working

  


  $ffmpeg -i input.wav -acodec copy -ss 1 -to 3 input_slice.wav
$ffmpeg -i input_slice.wav -ac 1 -c:a libfdk_aac -profile:a aac_he -vbr 2 ffmpeg_export.m4a


  


  mediainfo output :

  


  General
Complete name                            : ffmpeg_export.m4a
Format                                   : MPEG-4
Format profile                           : Apple audio with iTunes info
Codec ID                                 : M4A  (isom/iso2)
File size                                : 11.2 KiB
Duration                                 : 2 s 112 ms
Overall bit rate mode                    : Constant
Overall bit rate                         : 43.6 kb/s
Writing application                      : Lavf58.29.100

Audio
ID                                       : 1
Format                                   : AAC LC SBR
Format/Info                              : Advanced Audio Codec Low Complexity with Spectral Band Replication
Commercial name                          : HE-AAC
Format settings                          : NBC
Codec ID                                 : mp4a-40-5
Duration                                 : 2 s 112 ms
Duration_LastFrame                       : -25 ms
Bit rate mode                            : Constant
Bit rate                                 : 39.9 kb/s
Channel(s)                               : 1 channel
Channel layout                           : C
Sampling rate                            : 44.1 kHz
Frame rate                               : 21.533 FPS (2048 SPF)
Compression mode                         : Lossy
Stream size                              : 10.3 KiB (91%)
Default                                  : Yes
Alternate group                          : 1


  


  I already tried moving metadata to the front with -movflags faststart on the broken file and it didn't make a difference.

  


• Remove unnecessary use of avcodec_close().

  27 mai 2020, par Anton Khirnov

  Remove unnecessary use of avcodec_close().
  Replace it with avcodec_free_context() or drop it completely as
  
  appropriate.
  

  • [DH] libavcodec/avrndec.c
  • [DH] libavcodec/smvjpegdec.c
  • [DH] libavcodec/tests/options.c
  • [DH] libavfilter/vf_subtitles.c
  • [DH] libavfilter/vf_uspp.c
  • [DH] tests/api/api-band-test.c
  • [DH] tests/api/api-flac-test.c
  • [DH] tests/api/api-h264-test.c
  • [DH] tests/api/api-seek-test.c

• Using ffmpeg dll's from a windows 32 bit app

  8 avril 2020, par Derek

  I am trying to use ffmpeg via dll calls from a win32 app (compiled in clarion)

  



  I transcoded the example file encode_video.c and that worked 100% however I was left with a .h264 file instead of a .mp4 file.

  



  I then transcoded the example muxing.c however it crashes and I am at a loss for options.

  



  Any help would be most appreciated.

  



  Encode_mp4 ROUTINE
! avformat_alloc_output_context2 *******************************************************************************************
file_name = 'myvideo.mp4'
! Try guess format from filename
if CHECK_STACK then ds_SaveStack .
Result = avformat_alloc_output_context2(ThisPtrPtr, 0, NullCString, file_name);
if CHECK_STACK then ds_TestStack .
if Result < 0
    ds_OutputDebugString('avformat_alloc_output_context2 Try guess format failed, try mpeg', TRUE)
    CString1 = 'mpeg'
    if CHECK_STACK then ds_SaveStack .
    Result = avformat_alloc_output_context2(ThisPtrPtr, 0, CString1, file_name);
    if CHECK_STACK then ds_TestStack .
    if Result < 0
        ds_OutputDebugString('avformat_alloc_output_context2 failed', TRUE)
        stop('Could not allocate output format context')
        exit
    end
end
formater_ctxt &= (ThisPtrPtr)
!ds_OutputDebugString('formater_ctxt=' & address(formater_ctxt), TRUE)
assert(not(formater_ctxt &= NULL), 'Check AVFormatContext formater_ctxt')
do VerifyFormatContext
assert(formater_ctxt.oformat > 0, 'Check AVFormatContext formater_ctxt.oformat')
formater &= (formater_ctxt.oformat)
do VerifyFormat
ds_OutputDebugString('avformat_alloc_output_context2 OK', TRUE)

! avcodec_find_encoder *******************************************************************************************
if CHECK_STACK then ds_SaveStack .
encoder &= avcodec_find_encoder(formater.video_codec)
if CHECK_STACK then ds_TestStack .
if encoder &= NULL
    ds_OutputDebugString('avcodec_find_encoder failed', TRUE)
    stop('Could not find encoder')
    exit
end
do VerifyEncoder
ds_OutputDebugString('avcodec_find_encoder OK', TRUE)

! avformat_new_stream *******************************************************************************************
if CHECK_STACK then ds_SaveStack .
stream &= avformat_new_stream(formater_ctxt, encoder)
if CHECK_STACK then ds_TestStack .
if stream &= NULL 
    ds_OutputDebugString('avformat_new_stream failed', TRUE)
    stop('Could not create new stream')
    exit
end
do VerifyStream
stream.id = formater_ctxt.nb_streams-1
ds_OutputDebugString('avformat_new_stream OK', TRUE)

! avcodec_alloc_context3 *******************************************************************************************
if CHECK_STACK then ds_SaveStack .
encoder_ctxt &= avcodec_alloc_context3(encoder)
if CHECK_STACK then ds_TestStack .
if encoder_ctxt &= NULL 
    ds_OutputDebugString('avcodec_alloc_context3 failed', TRUE)
    stop('Could not allocate video codec context')
    exit
end
do VerifyEncoderContext
ds_OutputDebugString('avcodec_alloc_context3 OK', TRUE)

! Video settings *******************************************************************************************
do InitVideoSettings

assert(AV_CODEC_FLAG_GLOBAL_HEADER = bshift(1, 22), 'Check AV_CODEC_FLAG_GLOBAL_HEADER')
if band(formater.flags, AVFMT_GLOBALHEADER)
   encoder_ctxt.flags = bor(encoder_ctxt.flags, AV_CODEC_FLAG_GLOBAL_HEADER) !avctx->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
end

! avcodec_open2 *******************************************************************************************
if CHECK_STACK then ds_SaveStack .
Result = avcodec_open2(encoder_ctxt, encoder, 0)
if CHECK_STACK then ds_TestStack .
if Result < 0
    ds_OutputDebugString('avcodec_open2 failed.  Result=' & Result, TRUE)
    stop('Could not open codec')
    exit
end
ds_OutputDebugString('avcodec_open2 OK', TRUE)

! av_frame_alloc *******************************************************************************************
if CHECK_STACK then ds_SaveStack .
frame &= av_frame_alloc();
if CHECK_STACK then ds_TestStack .
if frame &= NULL
    ds_OutputDebugString('av_frame_alloc failed', TRUE)
    stop('Could not allocate video frame')
    exit
end
do VerifyFrame
frame.format = encoder_ctxt.pix_fmt
frame.width = encoder_ctxt.width
frame.height = encoder_ctxt.height
ds_OutputDebugString('av_frame_alloc OK', TRUE)

! av_frame_get_buffer *******************************************************************************************
if CHECK_STACK then ds_SaveStack .
Result = av_frame_get_buffer(frame, 32)
if CHECK_STACK then ds_TestStack .
if Result < 0
    ds_OutputDebugString('av_frame_get_buffer failed', TRUE)
    stop('Could not allocate video frame buffer Error = ' & Result)
    exit
end
do VerifyFrameBuffer
ds_OutputDebugString('av_frame_get_buffer OK', TRUE)

!frame->data offset=0  Array[8] of *int8_t
UseData0 &= (frame.data[1])
UseData1 &= (frame.data[2])
UseData2 &= (frame.data[3])

if CHECK_STACK then ds_SaveStack .
Result = avcodec_parameters_from_context(stream.codecpar, encoder_ctxt);
if CHECK_STACK then ds_TestStack .
if Result < 0
    ds_OutputDebugString('avcodec_parameters_from_context failed', TRUE)
    stop('Could not initialize stream parameters')
    exit
end
ds_OutputDebugString('avcodec_parameters_from_context OK', TRUE)

! av_dump_format *******************************************************************************************
ds_OutputDebugString('before call to av_dump_format  file_name=' & file_name, TRUE)
av_dump_format(formater_ctxt, 0, file_name, 1)


  



  I get a crash at last line - call to av_dump_format()

  



  If I comment this code then I get a crash on the very next lib call :

  



      ! avio_open *******************************************************************************************
if not(band(formater.flags, AVFMT_NOFILE)) 
    ds_OutputDebugString('before call to avio_open  file_name=' & file_name, TRUE)
    ThisInt &= address(formater_ctxt.pb)
    Result = avio_open(ThisInt, file_name, AVIO_FLAG_WRITE)


  



  Strangely if I comment the setup call to av_log_set_callback(my_log_callback) then the crash moves down to the next lib call : avformat_write_header