Opened 5 years ago

Closed 5 years ago

#5891 closed defect (invalid)

"-t" not applied to streams when using channelsplit filter

Reported by: Matthew Austin Owned by:
Priority: normal Component: undetermined
Version: unspecified Keywords:
Cc: Blocked By:
Blocking: Reproduced by developer: no
Analyzed by developer: no


Summary of the bug:
I was using volumedetect to check each channel of a file to ensure that program start handles were mute, and got misleading readings when the incoming audio was split (using channelsplit). I have fixed my code by using atrim instead of -t but though the inconsistency was worth highlighting.

How to reproduce:

(Any stereo audio source)
ffmpeg -ss 149 -i [stereo wav] -filter_complex "[0:0] channelsplit=channel_layout=2c [A1] [A2], [A2] anullsink,  [A1] volumedetect"  -t 0.96 -vn -f null -
Results in:
[Parsed_volumedetect_2 @ 0000000002a463a0] n_samples: '''135634560'''
[Parsed_volumedetect_2 @ 0000000002a463a0] mean_volume: -25.3 dB
[Parsed_volumedetect_2 @ 0000000002a463a0] max_volume: -7.7 dB
[Parsed_volumedetect_2 @ 0000000002a463a0] histogram_7db: 57
[Parsed_volumedetect_2 @ 0000000002a463a0] histogram_8db: 40871
[Parsed_volumedetect_2 @ 0000000002a463a0] histogram_9db: 98220

ffmppeg -ss 149 -i [stereo wav] -filter_complex "[0:0] channelsplit=channel_layout=2c [A1] [A2], [A2] anullsink,  [A1] atrim=start=0:duration=0.96, volumedetect"  -vn -f null -
results in:
[Parsed_volumedetect_3 @ 00000000003400c0] n_samples: '''46080'''
[Parsed_volumedetect_3 @ 00000000003400c0] mean_volume: -91.0 dB
[Parsed_volumedetect_3 @ 00000000003400c0] max_volume: -91.0 dB
[Parsed_volumedetect_3 @ 00000000003400c0] histogram_91db: 46080

ffmpeg version N-81894-g54220ce
Zeranoe build

Patches should be submitted to the ffmpeg-devel mailing list and not this bug tracker.

Change History (3)

comment:1 by Carl Eugen Hoyos, 5 years ago

Please provide the actual command line that allows to reproduce the issue together with the complete, uncut console output to make this a valid ticket.

comment:2 by Nicolas George, 5 years ago

This is the expected behaviour: -t is an output option, it affects the processing after the filters.

Also, using sinks in filter graphs is not very well supported for now. To isolate a channel, you would probably be better off using -af pan.

comment:3 by Carl Eugen Hoyos, 5 years ago

Resolution: invalid
Status: newclosed
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