Re: [FFmpeg-devel] [PATCH 1/5] avcodec/mjpegdec: Always reset got_picture at the beginnig of decoding

From: Michael Niedermayer <michael@niedermayer.cc>
To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
Subject: Re: [FFmpeg-devel] [PATCH 1/5] avcodec/mjpegdec: Always reset got_picture at the beginnig of decoding
Date: Sat, 16 Apr 2022 00:15:35 +0200
Message-ID: <20220415221535.GO2829255@pb2> (raw)
In-Reply-To: <AS8PR01MB7944E105BE990A5D01EF89208FEF9@AS8PR01MB7944.eurprd01.prod.exchangelabs.com>

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On Thu, Apr 14, 2022 at 05:56:30PM +0200, Andreas Rheinhardt wrote:
> Said field is set when parsing a SOF; yet a picture is only allocated
> if skip_frame is != AVDISCARD_ALL. This leads to a crash in the
> following case: If a jpeg is split into two parts, the first containing
> everything before the scans including the SOF and the second part
> containing the rest, and the first part is sent to the decoder with
> skip_frame set to AVDISCARD_ALL, got_picture is set, yet no picture
> is allocated. If the next part is sent with skip_frame set to
> AVDISCARD_NONE, the code presumes that a picture has been allocated,
> although it hasn't leading to segfaults.
> 
> Fix this by resetting got_picture at the beginning of decoding.
> 
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
> ---
> This patch presumes that there is not use-case for partitioning
> the data corresponding to a single AVFrame accross multiple packets.
> I am not certain whether this is actually true, in particular
> wrt interlaced input where it might be common to put the data for
> one field into one packet.
> Anyway, no such use is covered by FATE.

This changes timestamps slightly for:
./ffmpeg -an -i ~/tickets/1915/m_noint.avi -an -bitexact -f framecrc -t 1 -

not sure thats intended

thx

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

Into a blind darkness they enter who follow after the Ignorance,
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to the Knowledge alone. -- Isha Upanishad

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