[FFmpeg-devel] [PATCH 16/21] fftools/ffmpeg: rework audio-decode timestamp handling

[Michael Niedermayer]

On Thu, Apr 27, 2023 at 04:25:56PM +0200, Anton Khirnov wrote:
> Stop using InputStream.dts for generating missing timestamps for decoded
> frames, because it contains pre-decoding timestamps and there may be
> arbitrary amount of delay between input packets and output frames (e.g.
> dependent on the thread count when frame threading is used). It is also
> in AV_TIME_BASE (i.e. microseconds), which may introduce unnecessary
> rounding issues.
> 

> New code maintains a timebase that is the inverse of the LCM of all the
> samplerates seen so far, and thus can accurately represent every audio

if the LCM fits in int32

This can hit some pathologic cases though
consider a 192khz stream that starts with a damaged packet thats read as 11.197 khz
lcm of 192000 and 11197 > 2^31 so the whole stream will then be stuck with 11.197khz
that seems like a bad choice
the code should favor standard sample rates as well as the higher sample rate if
the lcm is not representable

also if lets say there are 48khz and 48.001khz where again lcm doesnt work 
then a multiple of 48khz may be a better choice than either itself

also what happens if the audio timestamps are known more precissely than
the audio sample rate ?

thx

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Opposition brings concord. Out of discord comes the fairest harmony.
-- Heraclitus
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