Opened 5 years ago

Closed 5 years ago

#7932 closed defect (needs_more_info)

tee muxer: produces incorrect start_time, PTS

Reported by: sbalko Owned by:
Priority: normal Component: avformat
Version: git-master Keywords: tee
Cc: anna@zfaas.com, joshua@zfaas.com Blocked By:
Blocking: Reproduced by developer: no
Analyzed by developer: no

Description

Summary of the bug:
The tee muxer changes the PTS times (and hence, the start_time). That is, when we transcode an input video (https://drive.google.com/file/d/1qM40ZzOa10HJY7vZt0b-bx191eYBqqM_/view?usp=sharing, "Big Buck Bunny" WebM trailer) directly into MP4 like so:

ffmpeg -t 3 -i bunny.webm -vcodec libx264 -map 0:v bunny1.mp4

...we get an output video with a start_time property of 0.000000. In contrast, when using the "tee" muxer (for the sake of simplicity, with a single output only) like so:

ffmpeg -t 3 -i bunny.webm -vcodec libx264 -map 0:v -f tee "[f=mp4]bunny2.mp4"

...we get an output video, where the start_time property is 0.080000. We confirmed that both videos have the same number of frames, where the pkt_pts_time properties of bunny2.mp4 are +0.08 sec shifted.

How to reproduce:

ffmpeg version 3.4.6-0ubuntu0.18.04.1 Copyright (c) 2000-2019 the FFmpeg developers
built with gcc 7 (Ubuntu 7.3.0-16ubuntu3)

We can also reproduce this issue with a more recent FFmpeg build:

ffmpeg version N-93945-g02333fe394 Copyright (c) 2000-2019 the FFmpeg developers
built with gcc 7 (Ubuntu 7.4.0-1ubuntu1~18.04)

Attachments (1)

bunny.webm (2.1 MB ) - added by sbalko 5 years ago.
Big Buck Bunny trailer (WebM)

Change History (4)

by sbalko, 5 years ago

Attachment: bunny.webm added

Big Buck Bunny trailer (WebM)

comment:1 by sbalko, 5 years ago

...also attached the sample input video file to reproduce the issue.

comment:2 by Cigaes, 5 years ago

I suspect the -avoid_negative_ts option us responsible here. Does setting it to 1 for MP4 produce the same effect as tee? And setting to 0 for tee produce the same effect as MP4?

comment:3 by Carl Eugen Hoyos, 5 years ago

Keywords: start_time pkt_pts_time removed
Resolution: needs_more_info
Status: newclosed
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