On Thu, Aug 14, 2014 at 12:24:47PM +0200, Christophe Gisquet wrote: > Hi, > > the attached patch seems to fix ticket #3773, but streamcopy is such a > core feature of ffmpeg that I assume I'm missing a use case or > incorrectly handle the buffers referencing. > > Another note is that this patch was developed without a memory tracer > like valgrind: I have just validated that the test case doesn't crash > and passes fate-h264-bsf-mp4toannexb. > > Last point, I think this bug raises a few questions/issues: > - API may not be abundantly clear that AVPacket::data is refcounted > and should not be meddled with directly; > - For lack of a way to do it, ffmpeg.c streamcopy meddles with AVPacket::data; > - AVPacket::side_data is not ref-counted; because of such things as > av_format_inject_global_side_data, it could make sense to have it > separate from AVPacket::data ref-counting. > > That last point is probably a major, API-breaking, undertaking. I have > no plan to start on it, in particular because I feel unqualified for > it. > > Best regards, > -- > Christophe
> ffmpeg.c | 2 ++ > 1 file changed, 2 insertions(+) > f1a906a5c330dff16b266f80e14e9f1727a3a3bf > 0001-ffmpeg-fix-streamcopy-with-side-data.patch > From 7848e2eed0780d5d2b3190b90174d580257a7ec9 Mon Sep 17 00:00:00 2001 > From: Christophe Gisquet <christophe.gisq...@gmail.com> > Date: Wed, 13 Aug 2014 18:40:17 +0200 > Subject: [PATCH] ffmpeg: fix streamcopy with side data > > The issue is that, when the main packet data buffer is changed, streamcopy > uses a temporary new packet to store that buffer, frees the old packet, and > replace it with the new packet. > > However, in doing so, it forgets about the side data, which gets freed, but > is still needed and referenced. Then, when the packet gets freed again in > the normal code path, it attempts to free its side data which has already > been freed. > > Therefore, simply avoid the first free on side data by removing that side > data from the packet. > > Fixes ticket #3773. patch looks correct applied thanks [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB The greatest way to live with honor in this world is to be what we pretend to be. -- Socrates
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