> On Thu, May 31, 2018 at 10:11:38AM +0000, Eran Kornblau wrote: > > > > > > -----Original Message----- > > > From: ffmpeg-devel [mailto:ffmpeg-devel-boun...@ffmpeg.org] On > > > Behalf Of Eran Kornblau > > > Sent: Friday, May 25, 2018 4:40 PM > > > To: FFmpeg development discussions and patches > > > <ffmpeg-devel@ffmpeg.org> > > > Subject: [FFmpeg-devel] qt-faststart bug near 4GB > > > > > > Hi all, > > > > > > We encountered a rather extreme edge case with qt-faststart - we > > > transcoded some video with ffmpeg, and the offset of the last video frame > > > in the resulting mp4 was slightly less than 4GB. > > > Since it was less than 4GB, ffmpeg used an 'stco' atom and not a 'co64' > > > atom. > > > When we ran qt-faststart on this file, it added the moov atom size to all > > > offsets in the 'stco' atom, causing an overflow in the offsets of the > > > frames close to the end of the file. The end of the video was therefore > > > corrupt and could not be played. > > > I think the solution here is to 'upgrade' the 'stco' atom to 'co64' if > > > such an edge case happens. However, looking at the code of qt-faststart, > > > I see that it doesn't actually parse the atom tree, but rather looks for > > > the strings 'stco' / 'co64'. Changing 'stco' to 'co64' requires updating > > > the size of all the atom in which it's contained (moov, trak, mdia etc.) > > > Therefore, such a change would probably be more of a rewrite of this > > > utility than a patch, so wanted to check whether anyone has any thoughts > > > on this before I start writing... > > > > > Attaching the patch for this issue. > > As expected, it required significant changes... hope you will like it > > :) > > > > Thanks! > > > > Eran > > about the AV_WB* macros, i like them alot :) but this seems not to apply > cleanly: > > Applying: qt-faststart - stco offset bug fix Using index info to reconstruct > a base tree... > M tools/qt-faststart.c > Falling back to patching base and 3-way merge... > Auto-merging tools/qt-faststart.c > CONFLICT (content): Merge conflict in tools/qt-faststart.c > error: Failed to merge in the changes. > Patch failed at 0001 qt-faststart - stco offset bug fix Use 'git am > --show-current-patch' to see the failed patch When you have resolved this > problem, run "git am --continue". > If you prefer to skip this patch, run "git am --skip" instead. > To restore the original branch and stop patching, run "git am --abort". > Sorry Michael, I forgot to revert the previous patch before committing. Attaching a fixed patch.
Thanks Eran > [...] > > -- > Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB > > Into a blind darkness they enter who follow after the Ignorance, they as if > into a greater darkness enter who devote themselves to the Knowledge alone. > -- Isha Upanishad >
0001-qt-faststart-stco-offset-bug-fix.patch
Description: 0001-qt-faststart-stco-offset-bug-fix.patch
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