1022762 - Old versions of ffmpeg/avconv produce invalid WebM files with negative block timestamps

Status: RESOLVED WORKSFORME

(Core :: Audio/Video, defect)

Description

[Axel Viala]

Precisions:
The video was on my computer.

Here the video data:
$> mediainfo Meetup_Debian_GSOC_Debian_by_Nicolas_Dandrimont.webm 
General
Unique ID                                : 177458358920729835901762565335362572187 (0x85813C9A84105948E136FAEDDC240F9B)
Complete name                            : Meetup_Debian_GSOC_Debian_by_Nicolas_Dandrimont.webm
Format                                   : WebM
Format version                           : Version 2
File size                                : 116 MiB
Duration                                 : 19mn 17s
Overall bit rate mode                    : Variable
Overall bit rate                         : 843 Kbps
Writing application                      : Lavf54.20.4
Writing library                          : Lavf54.20.4

Video
ID                                       : 1
Format                                   : VP8
Codec ID                                 : V_VP8
Duration                                 : 19mn 17s
Bit rate                                 : 689 Kbps
Width                                    : 1 280 pixels
Height                                   : 720 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 30.000 fps
Compression mode                         : Lossy
Bits/(Pixel*Frame)                       : 0.025
Stream size                              : 95.0 MiB (82%)
Language                                 : English
Default                                  : Yes
Forced                                   : No

Audio
ID                                       : 2
Format                                   : Vorbis
Format settings, Floor                   : 1
Codec ID                                 : A_VORBIS
Duration                                 : 19mn 17s
Bit rate mode                            : Variable
Bit rate                                 : 112 Kbps
Channel(s)                               : 2 channels
Sampling rate                            : 44.1 KHz
Compression mode                         : Lossy
Delay relative to video                  : 1mn 5s
Stream size                              : 15.5 MiB (13%)
Writing library                          : libVorbis (Schaufenugget) (20101101 (Schaufenugget))
Language                                 : English
Default                                  : Yes
Forced                                   : No
Writing application                      : Lavc54.35.0


Attachment:
Comparison of behavior with chromium.

Comment 1

[Axel Viala]

Attachment: Image to show the behaviour in Chromium and in Firefox.

Comment 2

[Sylvestre Ledru [:Sylvestre]]

I have the same problem with Firefox 31.

Comment 3

[Axel Viala]

video made with:

$> avconv -i video.f4c -c:v libvpx -qmin 0 -qmax 50 -crf 10 -b:v 2M video.webm

Comment 4

[Matthew Gregan [:kinetik]]

Can you please post links to the videos that will not play?  Alternatively, you can attach the first ~1MB of the video to the bug.

Comment 5

[Axel Viala]

Link to download the video:
https://weby.kokakiwi.net/Meetup_Debian_GSOC_Debian_by_Nicolas_Dandrimont.webm

Thanks. :)

Comment 6

[Matthew Gregan [:kinetik]]

Thanks Axel!  This seems to be another case of bug 868797, which is ffmpeg/avconv producing files that violate the spec (but that some other players happen to support).  mkvinfo -v shows:

|+ Cluster
| + Cluster timecode: 0.000s
| + SimpleBlock (key, track number 2, 1 frame(s), timecode 18446744027.136s = -00:00:00.003)
|  + Frame with size 1
| + SimpleBlock (key, track number 2, 1 frame(s), timecode 0.000s = 00:00:00.000)
|  + Frame with size 1

It also writes other crazy stuff into the file, such as:

|  + Default duration: 0.333ms (3000.003 frames/fields per second for a video track)

...which we (and probably most other players) ignore.

Since bug 868797 covers a potential change to Firefox to accept these files, I'll make this bug an evang bug for ffmpeg/avconv so that we can chase up when this bug was introduced and when it was/will be fixed.

Comment 7

[Matthew Gregan [:kinetik]]

This should be the change that fixes the bug:

http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=b08273c9ca8b91d03133f9fbef100bbd3cd8e271

Comment 8

[Matthew Gregan [:kinetik]]

...which corresponds to FFmpeg 1.1 aka libavformat 54.59.106.

And Axel's file was produced with 54.20.4.  So I'll close this as "fixed upstream", and leave bug 868797 for fixing our reporting of the broken file.