[FFmpeg-devel] [PATCH 0/2] Fix ALAC encoder for 24bps

Christophe Gisquet christophe.gisquet at gmail.com
Mon Aug 18 10:02:22 CEST 2014


2014-08-17 19:09 GMT+02:00 Christophe Gisquet <christophe.gisquet at gmail.com>:
> It would possible to detect bitstreams before this change and achieve
> correct decoding if need be.

So after further exploration, you can't really detect this:
- there's no metadata for the alac bitstream
- the container one may be stripped or added while importing a valid
alac bitstream
- it may be possible to detect this when an overflow occurs (ie
samples have a larger magnitude than expected) but I bet this doesn't
always occur
- I don't see a crc or whatever allowing to identify if the stream was
incorrectly decoded

Anyway, it was suggested to add a command-line option to be able to
force this. Please confirm the steps needed:
- Add a new flag in workaround_bugs (eg FF_BUG_ALAC_MATRIXING valued at 32768)
- Add an option for this (in options_table.h)
- Bump micro? We're at 56.0.101. Should that become 56.0.102 or
56.1.xx (100? 0?)


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