glitchy reading of lagarith 1.3.27 streams

[Christoph Rackwitz]

Summary of the bug: appears to decode the wrong I-frames of most recent lagarith video. also produces black frames where there were none. generally glitchy. output completely blank when choosing -c:v libx264 for this input.

How to reproduce:

% ffmpeg -i lagarith-1.3.27-black-frames-and-off-by-ones.avi -an -c:v qtrle lagarith-1.3.27-black-frames-and-off-by-ones.mov

ffmpeg version N-66352-g33c752b Copyright (c) 2000-2014 the FFmpeg developers
  built on Sep 19 2014 23:23:41 with gcc 4.9.1 (GCC)

[Christoph Rackwitz]

I've attached a generating python script that requests a codec picker, where Lagarith (video for windows) should be chosen.

the attached .avi file is 25fps 3.0 seconds and should be black, "frame 1", then "frame2".

the attached qtrle .mov file is the output. I see the black frame briefly. the video isn't 3.0 seconds long anymore.

the attached .txt file is a copy of the console output.

I've used the most recent nightly build from ​http://ffmpeg.zeranoe.com/builds/.

[Carl Eugen Hoyos]

Could you test the following command line? I believe the issue is not lagarith-related, FFplay also works correctly for the sample afaict.

$ ffmpeg -i lagarith-1.3.27-black-frames-and-off-by-ones.avi​ -vf fps=25 -vcodec mpeg4 out.mov

[Christoph Rackwitz]

ffprobe on the output: Duration: 00:00:02.04, start: 0.000000, bitrate: 133 kb/s
see attached file comment-2.mov

[Carl Eugen Hoyos]

Your input video has three frames, all three are decoded correctly, you can test for example with:

$ ffmpeg -vsync 0 -i lagarith-1.3.27-black-frames-and-off-by-ones.avi​ out%1d.png

FFmpeg does not work very well for first / last frames of vfr video, this is covered by several other tickets, among them #1578, (more similar to this problem) #2674 and #3052. You can basically choose if you want to have a "short" first frame with -r 25 or a "short" last frame with -vf fps=25.
A patch for fps exists:
​http://thread.gmane.org/gmane.comp.video.ffmpeg.devel/180754/focus=180758
It probably fixes your issue but was not accepted yet.

[Christoph Rackwitz]

I understand the problem is variable frame rate. I'd really like to have this reproduced faithfully. I can't choose between losing frames at either end. Thanks for taking a look and linking related tickets. I'll have to wait for a fix then.

[Carl Eugen Hoyos]

It is possible that concatenating your input video with a single black frame works fine, I am sure it is not difficult to find a workaround.

[llogan]

This was probably fixed by 9f6d48d696d679de77e8cb513d5f64cd708ed86f. Please test.

[Carl Eugen Hoyos]

The duration of the last frame is still wrong with both -r and -vf fps, see tickets #2674 and #3052.

[Carl Eugen Hoyos]

Still reproducible after #1578 and #3052 were fixed, Michael posted a patch:
​http://ffmpeg.org/pipermail/ffmpeg-devel/2014-November/165583.html

[Carl Eugen Hoyos]

Fixed by Michael in 98c7729c133e801889adc3f6527ff271b2df73b5