[FFmpeg-devel] [PATCH 2/2] avcodec/mjpegdec: postpone calling ff_get_buffer() until the SOS marker

[Michael Niedermayer]

On Wed, Apr 21, 2021 at 02:40:55PM -0300, James Almer wrote:
> With JPEG-LS PAL8 samples, the JPEG-LS extension parameters signaled with
> the LSE marker show up after SOF but before SOS. For those, the pixel format
> chosen by get_format() in SOF is GRAY8, and then replaced by PAL8 in LSE.
> This has not been an issue given both pixel formats allocate the second data
> plane for the palette, but after the upcoming soname bump, GRAY8 will no longer
> do that. This will result in segfauls when ff_jpegls_decode_lse() attempts to
> write the palette on a buffer originally allocated as a GRAY8 one.
> 
> Work around this by calling ff_get_buffer() after the actual pixel format is
> known.
> 
> Signed-off-by: James Almer <jamrial at gmail.com>
> ---
> With this, the removal of AV_PIX_FMT_FLAG_PSEUDOPAL will no longer generate
> segfauls.
> I can't test hwaccels like vaapi to ensure things still work as inteded, seeing
> i also had to move the call to start_frame().
> 
> Better solutions are very much welcome.
> 
>  libavcodec/jpeglsdec.c |  6 ++--
>  libavcodec/mjpegdec.c  | 72 +++++++++++++++++++++++-------------------
>  libavcodec/mjpegdec.h  |  2 ++
>  3 files changed, 43 insertions(+), 37 deletions(-)

this causes a change in one timestamp on decode of:

./ffmpeg -ss 1.2 -i ~/tickets/3245/bad-example.mov -vframes 10 outnew.avi
./ffmpeg -i out.avi -f framecrc /tmp/crc

--- /tmp/crc	2021-04-22 14:56:47.981354127 +0200
+++ /tmp/crcnew	2021-04-22 14:56:32.373271448 +0200
@@ -23,8 +23,8 @@
 0,          4,          4,        1,   622080, 0xf24584d3
 1,       8064,       8064,     1152,     4608, 0x70bf8dc7
 1,       9216,       9216,     1152,     4608, 0xd00f873a
+0,          5,          5,        1,   622080, 0x5f8afe7d
 1,      10368,      10368,     1152,     4608, 0xd45d84b8
-0,          6,          6,        1,   622080, 0x5f8afe7d
 1,      11520,      11520,     1152,     4608, 0x64b5866e
 1,      12672,      12672,     1152,     4608, 0x36a18daf
 0,          7,          7,        1,   622080, 0x09918d93

 
I did not investigate why or if that is even a issue, just wanted to
report it

thx

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

The smallest minority on earth is the individual. Those who deny 
individual rights cannot claim to be defenders of minorities. - Ayn Rand
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