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• Segmenting .flac files with ffmpeg truncates audio but not file length

  5 avril 2022, par Yan White

  I am trying to get Twitter spaces audio (.ts) files into a format I can easily edit, on OSX.

  


  So far I was able to convert the files in bulk to .flac with this :

  


  for i in *.ts;
do name=`echo "$i" | cut -d'.' -f1`
echo "$name"
ffmpeg -i "$i" -sample_fmt s16 -ar 41000 "${name}.flac"
done


  


  That worked, and reduced the file sizes somewhat, but..
Because most of the files are around 7 hours long, my editor of choice cannot process that much audio in one file.

  


  So I looked around and was able to find this command to segment the files into 3hr long sections.

  


  ffmpeg -i space-1OdKrBealBqKX_0.flac -map 0 -f segment -segment_time 10800 -c copy space-1OdKrBealBqKX_0__%03d.flac


  


  This works, but each file contains as much empty / silent space at the end as the orginal file. That's going to be a problem for sharing with a team that will help edit these files, as each file has the original file's length and file size. There are a lot of files.
The audio segments and naming did work though.

  


  How to truncate the actual length of the file to the audio segment ?

  


  Caveat : I am no expert on any of these matters, I just managed to google and get this far, so if someone knows and wants to provide working code that would be very much appreciated !

  


• avfilter/af_agate : Honour query_formats API, fix segfault

  21 septembre 2021, par Andreas Rheinhardt

  avfilter/af_agate : Honour query_formats API, fix segfault
  The sidechaingate filter wants its main input and its (only) output
  
  to have the same channel layout and number of channels ; yet it does
  
  not link them in its query_formats callback. Instead it sets the
  
  outlink to only accept the first offered choice for the main input's
  
  channel layout and then sets both inputs to independently accept
  
  any channel counts. The config_output callback then overwrote the
  
  outlink's channel layout and channels properties with the main input's,
  
  even though they may differ in case the first offered choice for
  
  the main input's channel layout turns out not to be the final one.
  Consider e.g. the following filtergraph :
  
  [in]aformat=channel_layouts=mono,aformat=channel_layouts=stereo|mono[out] ;\
  
  [out][in2]sidechaingate,stereotools
  
  The two aformats ensure that the first offered channel layout (stereo)
  
  will not be chosen for the input ; yet it is the only offered channel
  
  layout for the output of sidechaingate and will therefore be chosen
  
  by the query_formats framework. Because the sidechaingate outputs
  
  interleaved doubles which stereotools expects the output of
  
  sidechaingate appears to be suitable as input for stereotools without
  
  further conversions. Yet stereotools actually only receives a mono frame
  
  and therefore overreads its input buffer which leads to segfaults ;
  
  it can also lead to heap corruption because there can be writes beyond
  
  the end of the buffer, too.
  Fix this by linking the channel layouts of the main input and the output
  
  in query_formats and remove the code overwriting it in config_output.
  Reviewed-by : Paul B Mahol <onemda@gmail.com>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavfilter/af_agate.c

• configure : arm : Don't add -march= to the compiler if no preference was passed

  20 septembre 2021, par Martin Storsjö

  configure : arm : Don't add -march= to the compiler if no preference was passed
  If no —cpu= option was passed to configure, we detect what the
  
  compiler defaults to. This detected value was then fed back to the
  
  rest of the configure logic, as if it was an explicit choice.
  This breaks on Ubuntu 21.10 with GCC 11.1.
  Since GCC 8, it's possible to add configure extra features via the
  
   march option, like e.g. -march=armv7-a+neon. If the -mfpu= option
  
  is configured to default to 'auto', the fpu setting gets taken
  
  from the -march option.
  GCC 11.1 in Ubuntu seems to be configured to use -mfpu=auto. This
  
  has the effect of breaking any compilation command that specifies
  
   march=armv7-a, because the driver implicitly also adds -mfloat-abi=hard,
  
  and that combination results in this error :
      cc1 : error : ‘-mfloat-abi=hard’ : selected processor lacks an FPU
  One can compile successfully by passing e.g. -march=armv7-a+fp.
  Therefore, restructure configure. If no specific preference was set
  
  (and the 'cpu' configure variable was set as the output of
  
  probe_arm_arch), the value we tried to set via -march= was the same
  
  value that we just tried to detect as the compiler default.
  So instead, just try to detect what the compiler defaults to, with
  
  to allow setting other configure settings (such as 'fast_unaligned'),
  
  but don't try to spell out the compiler's default via the -march flag.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DH] configure