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• Removing both leading and trailing silence from m4a files using ffmpeg

  11 juin 2021, par Tejas Shah

  I have an audio file which has both leading and trailing silence and with the following specifics :

  



  Codec : MPEG AAC Audio (mp4a) Channels : Stereo Sample rate : 44100 Hz Bitrate : 253 kbps

  



  I want to remove the silences AND keep the quality intact.

  



  So far I've tried

  



  ffmpeg -i 1.m4a -af silenceremove=1:0.5:0:1:0.5:0 2.m4a 


  



  This is supposed to remove both the leading and trailing silences. 
But for some reason it doesn't remove the trailing silence. This seems to be a recurring problem. Found the following on another forum.

  



  http://ffmpeg-users.933282.n4.nabble.com/How-to-delete-digital-silence-tp4667256p4667356.html

  



  Also, ffmpeg reduces the bitrate to 128kbps. This I could fix by adding -ab 253k and making the command :

  



  ffmpeg -i 1.m4a -af silenceremove=1:0.5:0:1:0.5:0 -ab 253k 3.m4a 


  



  Now the problem is that the trailing silence isn't removed and when I want to process a batch of files I can't use the same bitrate (like 253kbps ) for every file. I'd like to know how VBR could be used for this case.

  



  I know I can use sox and use the silence and reverse features to trim the silences.

  



  http://digitalcardboard.com/blog/2009/08/25/the-sox-of-silence "Example 3 in this post"

  



  But sox has the following problems :

  



  

  1. It can't handle m4a files, I had to convert all files to mp3.

  


  2. When using the silence filter in sox it caps the bitrate at 128kbps.

     



     sox 1.mp3 2.mp3 silence 1 0.5 1% reverse silence 1 0.5 1% reverse


  


  


• avcodec/bitstream : Remove outdated comment

  29 août 2020, par Andreas Rheinhardt

  avcodec/bitstream : Remove outdated comment
  The comment referred to the INIT_VLC_USE_STATIC flag which has been
  
  removed in 2009 in 595324e143b57a52e2329eb47b84395c70f93087 ; the
  
  function it referred to was removed even earlier in commit
  
  83422c1940d963d395a64bee0cbb9c637192ce8c in 2008.
  Reviewed-by : Paul B Mahol <onemda@gmail.com>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavcodec/bitstream.c

• FFMPEG, faulty input with only a few keyframes ?

  9 août 2020, par browncatmegazord

  I have this video I can watch on MPC-HC alright, but I've been trying to re-encode it with FFMPEG to no avail.

  


  The video unerringly stops 5 minutes into the clip and freezes. Checking the key frames it would seem like the last keyframe is indeed at around the 5 minute mark, even though the video is completely watchable for its entire duration of upwards an hour. I've been looking into finding a way to repopulate the index of keyframes or something, but the answer eludes me.

  


  Both Handbrake and Premiere Pro fails to handle this video properly as well. Premiere Pro just imports it as though it's 5 minutes long, and Handbrake freezes when the encoding reaches the 5 minute mark.

  


  Even doing a -c copy would give me an output that terminates at the 5 minute mark.

  


  What can I do to fix this ?

  


  Edit : Added log as requested.

  


  ffmpeg version git-2020-02-27-9b22254 Copyright (c) 2000-2020 the FFmpeg developers
  built with gcc 9.2.1 (GCC) 20200122
  configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-fontconfig --enable-gnutls --enable-iconv --enable-libass --enable-libdav1d --enable-libbluray --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libtheora --enable-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-ffnvcodec --enable-cuda-llvm --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec --enable-dxva2 --enable-avisynth --enable-libopenmpt --enable-amf
  libavutil      56. 42.100 / 56. 42.100
  libavcodec     58. 73.102 / 58. 73.102
  libavformat    58. 39.101 / 58. 39.101
  libavdevice    58.  9.103 / 58.  9.103
  libavfilter     7. 77.100 /  7. 77.100
  libswscale      5.  6.100 /  5.  6.100
  libswresample   3.  6.100 /  3.  6.100
  libpostproc    55.  6.100 / 55.  6.100
[mov,mp4,m4a,3gp,3g2,mj2 @ 0000019d5f659b00] st: 0 edit list: 1 Missing key frame while searching for timestamp: 20
[mov,mp4,m4a,3gp,3g2,mj2 @ 0000019d5f659b00] st: 0 edit list 1 Cannot find an index entry before timestamp: 20.
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '[REDACTED].mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 1
    compatible_brands: isom
    creation_time   : 2009-07-27T12:06:40.000000Z
  Duration: 01:13:58.42, start: 0.000000, bitrate: 2671 kb/s
    Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p, 716x480 [SAR 8:9 DAR 179:135], 2504 kb/s, SAR 29127:32768 DAR 1007794:760071, 29.97 fps, 29.97 tbr, 48k tbn, 59.94 tbc (default)
    Metadata:
      rotate          : 0
      creation_time   : 2007-09-08T18:58:09.000000Z
      encoder         : AVC Coding
    Side data:
      displaymatrix: rotation of -0.00 degrees
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 159 kb/s (default)
    Metadata:
      creation_time   : 2009-07-27T12:06:47.000000Z
      handler_name    : GPAC ISO Audio Handler
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 @ 0000019d5f65de40] using SAR=8/9
[libx264 @ 0000019d5f65de40] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
[libx264 @ 0000019d5f65de40] profile High 4:4:4 Predictive, level 3.0, 4:2:0, 8-bit
[libx264 @ 0000019d5f65de40] 64 - core 159 - H.264/MPEG-4 AVC codec - Copyleft 2003-2019 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=0 mixed_ref=1 me_range=16 chroma_me=1 trellis=0 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=0 chroma_qp_offset=0 threads=9 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=0 weightp=2 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc=cqp mbtree=0 qp=0
Output #0, mp4, to '[REDACTED].mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 1
    compatible_brands: isom
    encoder         : Lavf58.39.101
    Stream #0:0(und): Video: h264 (libx264) (avc1 / 0x31637661), yuv420p(progressive), 716x480 [SAR 29127:32768 DAR 1007794:760071], q=-1--1, 29.97 fps, 11988 tbn, 29.97 tbc (default)
    Metadata:
      encoder         : Lavc58.73.102 libx264
      creation_time   : 2007-09-08T18:58:09.000000Z
    Side data:
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: N/A
      displaymatrix: rotation of -0.00 degrees
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 192 kb/s (default)
    Metadata:
      creation_time   : 2009-07-27T12:06:47.000000Z
      handler_name    : GPAC ISO Audio Handler
      encoder         : Lavc58.73.102 aac
frame= 9958 fps= 70 q=-1.0 Lsize=  960472kB time=00:11:13.32 bitrate=11685.6kbits/s speed=4.71x
video:944292kB audio:15836kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.035744%
[libx264 @ 0000015f858dde40] frame I:46    Avg QP: 0.00  size:113701
[libx264 @ 0000015f858dde40] frame P:9912  Avg QP: 0.00  size: 97026
[libx264 @ 0000015f858dde40] mb I  I16..4: 52.6% 10.7% 36.7%
[libx264 @ 0000015f858dde40] mb P  I16..4: 22.5%  5.5% 10.5%  P16..4: 31.8% 15.2% 11.1%  0.0%  0.0%    skip: 3.4%
[libx264 @ 0000015f858dde40] 8x8 transform intra:14.3% inter:40.9%
[libx264 @ 0000015f858dde40] coded y,uvDC,uvAC intra: 95.6% 84.9% 84.0% inter: 81.2% 83.0% 82.5%
[libx264 @ 0000015f858dde40] i16 v,h,dc,p: 53% 44%  2%  1%
[libx264 @ 0000015f858dde40] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 40% 47%  8%  1%  1%  1%  1%  1%  1%
[libx264 @ 0000015f858dde40] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 33% 44%  5%  3%  5%  4%  2%  3%  1%
[libx264 @ 0000015f858dde40] i8c dc,h,v,p: 12% 44% 43%  1%
[libx264 @ 0000015f858dde40] Weighted P-Frames: Y:1.0% UV:0.2%
[libx264 @ 0000015f858dde40] ref P L0: 59.1% 10.2% 27.8%  2.9%  0.0%
[libx264 @ 0000015f858dde40] kb/s:23281.49
[aac @ 0000015f85b5b880] Qavg: 182.070