Bug#783983: blender: VSE stretches video segments and uses incorrect video starting point

[Sergey Sharybin]

Hi,

This is likely due to official builds using FFmpeg and Debian's builds
using Libav library to handle video files.

It'll be cool if upstream Blender supported both Libav and FFmpeg version
at the same level, but it might also be simply a bug in Libav.. In order to
investigate this further it'll help a lot having exact files which
demonstrates the issue.

On Fri, 1 May 2015 16:08:17 -0400 sudoman at ninthfloor.org wrote:
> Package: blender
> Version: 2.72.b+dfsg0-3
> Severity: important
>
> Dear Maintainer,
>
> this was not an issue in wheezy but it is in jessie and experimental.
> the 2.74 binaries from blender.org do work.
>
> to reproduce the first aspect of this bug, select the video editing mode
> and add a long movie. increase the end point of playback range to 300000
> at the bottom of the screen. (this is the maximum.) then zoom out on the
> clips using the middle scroll wheel. then drag the green line over the
> clips and watch the playback in the upper right hand corner.
>
> what i expected to see was the full movie playing at a fast pace. what i
> saw was a shorter clip playing back (rather quickly) instead. if you
> click the play button, the video continues from that point at normal
> speed, which makes sense i guess. i'm not sure what happens when
> rendering from this state.
>
> the other bug occurs when opening a blender file from the wheezy or
> blender.org version of blender in the jessie (or experimental) version
> of blender. opening the file in blender.org's version works.
>
> in those files, i see the same issue as above, however i also see that
> the soft cuts points (i haven't tested hard cuts) seem to be ignored.
> even if a clip started from the middle of a movie in wheezy, it
> incorrectly starts from the beginning in the VSE when using jessie's
> version of blender. if i render that video, the starting point of the
> video clip is incorrect. audio seems to be unaffected.
>
> thanks for all of your hard work, dear maintainer!
> -Andrew
>
>
> -- System Information:
> Debian Release: 8.0
>   APT prefers stable-updates
>   APT policy: (500, 'stable-updates'), (500, 'stable'), (350,
'experimental'), (350, 'unstable')
> Architecture: amd64 (x86_64)
>
> Kernel: Linux 3.16.0-4-amd64 (SMP w/2 CPU cores)
> Locale: LANG=en_US.utf8, LC_CTYPE=en_US.utf8 (charmap=UTF-8)
> Shell: /bin/sh linked to /bin/dash
> Init: systemd (via /run/systemd/system)
>
> Versions of packages blender depends on:
> ii  blender-data                      2.72.b+dfsg0-3
> ii  fonts-droid                       1:4.4.4r2-6
> ii  libavcodec56                      6:11.3-1
> ii  libavdevice55                     6:11.3-1
> ii  libavformat56                     6:11.3-1
> ii  libavutil54                       6:11.3-1
> ii  libboost-date-time1.55.0          1.55.0+dfsg-3
> ii  libboost-filesystem1.55.0         1.55.0+dfsg-3
> ii  libboost-locale1.55.0             1.55.0+dfsg-3
> ii  libboost-regex1.55.0              1.55.0+dfsg-3
> ii  libboost-system1.55.0             1.55.0+dfsg-3
> ii  libboost-thread1.55.0             1.55.0+dfsg-3
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