From: Michael Niedermayer <michael@niedermayer.cc>
To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
Subject: Re: [FFmpeg-devel] [PATCH 16/21] fftools/ffmpeg: rework audio-decode timestamp handling
Date: Fri, 28 Apr 2023 13:42:17 +0200
Message-ID: <20230428114217.GE275832@pb2> (raw)
In-Reply-To: <20230427142601.2613-16-anton@khirnov.net>
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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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next prev parent reply other threads:[~2023-04-28 11:42 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-27 14:25 [FFmpeg-devel] [PATCH 01/21] fftools/ffmpeg: deprecate -adrift_threshold Anton Khirnov
2023-04-27 14:25 ` [FFmpeg-devel] [PATCH 02/21] fftools/ffmpeg: reduce access to OutputStream.enc_ctx Anton Khirnov
2023-04-27 14:25 ` [FFmpeg-devel] [PATCH 03/21] fftools/ffmpeg: drop OutputStream.pict_type Anton Khirnov
2023-04-27 14:25 ` [FFmpeg-devel] [PATCH 04/21] fftools/ffmpeg: drop OutputStream.error Anton Khirnov
2023-04-27 14:25 ` [FFmpeg-devel] [PATCH 05/21] fftools/ffmpeg: move OutputStream.packets_encoded to Encoder Anton Khirnov
2023-04-27 14:25 ` [FFmpeg-devel] [PATCH 06/21] fftools/ffmpeg: drop undocumented runtime debug-setting Anton Khirnov
2023-04-27 14:25 ` [FFmpeg-devel] [PATCH 07/21] fftools/ffmpeg_filter: make ifilter_parameters_from_frame() static Anton Khirnov
2023-04-27 14:25 ` [FFmpeg-devel] [PATCH 08/21] fftools/ffmpeg_filter: add filtergraph private data Anton Khirnov
2023-04-28 8:45 ` Nicolas George
2023-04-28 12:01 ` James Almer
2023-04-28 13:52 ` Nicolas George
2023-04-29 8:46 ` Nicolas George
2023-04-29 9:07 ` Anton Khirnov
2023-04-29 9:13 ` Nicolas George
2023-04-29 12:08 ` James Almer
2023-04-29 16:55 ` Nicolas George
2023-04-27 14:25 ` [FFmpeg-devel] [PATCH 09/21] fftools/ffmpeg_filter: make graph_desc private Anton Khirnov
2023-04-28 8:46 ` Nicolas George
2023-04-27 14:25 ` [FFmpeg-devel] [PATCH 10/21] fftools/ffmpeg_filter: factorize allocating InputFilter Anton Khirnov
2023-04-27 14:25 ` [FFmpeg-devel] [PATCH 11/21] fftools/ffmpeg_filter: add InputFilter private data Anton Khirnov
2023-04-28 8:47 ` Nicolas George
2023-04-27 14:25 ` [FFmpeg-devel] [PATCH 12/21] fftools/ffmpeg_filter: keep track of filtergraph input timebase Anton Khirnov
2023-04-28 8:48 ` Nicolas George
2023-04-27 14:25 ` [FFmpeg-devel] [PATCH 13/21] fftools/ffmpeg_filter: use correct timebase for filter EOF timestamp Anton Khirnov
2023-04-27 14:25 ` [FFmpeg-devel] [PATCH 14/21] fftools/ffmpeg: stop using packet pts for decoded audio frame pts Anton Khirnov
2023-04-27 14:25 ` [FFmpeg-devel] [PATCH 15/21] fftools/ffmpeg: set AVFrame.time_base for decoded frames Anton Khirnov
2023-04-27 14:25 ` [FFmpeg-devel] [PATCH 16/21] fftools/ffmpeg: rework audio-decode timestamp handling Anton Khirnov
2023-04-28 11:42 ` Michael Niedermayer [this message]
2023-04-28 13:11 ` Anton Khirnov
2023-04-28 19:24 ` Michael Niedermayer
2023-04-29 7:32 ` [FFmpeg-devel] [PATCH] " Anton Khirnov
2023-04-27 14:25 ` [FFmpeg-devel] [PATCH 17/21] fftools/ffmpeg: stop using InputStream.pts for generating video timestamps Anton Khirnov
2023-04-27 14:25 ` [FFmpeg-devel] [PATCH 18/21] fftools/ffmpeg_filter: stop using InputStream.pts for filter EOF ts Anton Khirnov
2023-04-27 14:25 ` [FFmpeg-devel] [PATCH 19/21] fftools/ffmpeg: drop InputStream.[next_]pts Anton Khirnov
2023-04-27 14:26 ` [FFmpeg-devel] [PATCH 20/21] fftools/ffmpeg: constify packets passed to decode*() Anton Khirnov
2023-04-27 14:26 ` [FFmpeg-devel] [PATCH 21/21] fftools/ffmpeg: always use the same path for setting InputStream.[next_]dts Anton Khirnov
2023-05-01 13:45 ` [FFmpeg-devel] [PATCH 01/21] fftools/ffmpeg: deprecate -adrift_threshold Anton Khirnov
2023-05-01 13:46 ` Paul B Mahol
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