Audio Offset

Discussion:

Audio Offset

YellowYeti

2017-11-04 22:55:42 UTC

Is anyone else experiencing an offset between audio & video lately?

I assume it's down to this new-ish method of splicing audio & video from
different sources.
I noticed it particularly on the latest 'have i got news for you' - with
around a second or so of offset between the audio & video.

It could be something to do with my setup, but before looking deeper,
does this happen for anyone else?

I know I can do the --no-hq-audio to prevent it - but if it's something
ro do with my setup I would rather get to the bottom of the problem.

Alan Milewczyk

2017-11-05 01:20:02 UTC

Permalink

Post by YellowYeti
Is anyone else experiencing an offset between audio & video lately?
I assume it's down to this new-ish method of splicing audio & video from
different sources.
I noticed it particularly on the latest 'have i got news for you' - with
around a second or so of offset between the audio & video.

YellowYeti

2017-11-05 12:52:04 UTC

Permalink

have I got news - downloaded on Friday, about 10:30 - offset of about 8
seconds between video and sound

graham norton - downloaded around 2am Saturday morning - offset of
around 0.4 seconds

re-downloaded today - no noticeable offset in either. I'll put it down
to problems at the bbc end for the moment.

Post by Alan Milewczyk

Just watched this episode of HIGNFY and there's no problem here. Not
noticed it on other downloads either.
A
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Alan Milewczyk

2017-11-05 18:19:30 UTC

Permalink

I downloaded both by timed batch file around 4am on Saturday morning,
looks like the problems gradually got sorted late at night.

A

Post by YellowYeti
have I got news - downloaded on Friday, about 10:30 - offset of about
8 seconds between video and sound
graham norton - downloaded around 2am Saturday morning - offset of
around 0.4 seconds
re-downloaded today - no noticeable offset in either. I'll put it down
to problems at the bbc end for the moment.

Post by Alan Milewczyk

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David Cantrell

2017-11-06 14:45:50 UTC

Permalink

Post by YellowYeti
Is anyone else experiencing an offset between audio & video lately?
I assume it's down to this new-ish method of splicing audio & video from
different sources.

I've not had that from stuff off iPlayer, it happens far more often with
stuff I record off-air!

--
David Cantrell | Pope | First Church of the Symmetrical Internet

More people are driven insane through religious hysteria than
by drinking alcohol. -- W C Fields

Ralph Corderoy

2017-11-06 15:07:08 UTC

Permalink

Hi,

Post by YellowYeti
Is anyone else experiencing an offset between audio & video lately?

I hadn't when he asked, but have since noticed it on last Thursday
night's _This Week_ downloaded on Friday. I adjusted the syncing
between the audio and video streams within the file to fix with
something like

ffmpeg -itsoffset 0.4 -i foo.mp4 -i foo.mp4 \
-map 0:1 -map 1:0 -c copy new-foo.mp4

IOW, have ffmpeg read the same file twice, taking the audio from one,
and the video from another, copying them into a new file, so no
transcoding, but with an "input time offset" applied to one of them of
0.4 s. The corrective delay is found through experimentation and adding
a `-to 00:00:30' after the `-c copy' helps that by quickly producing
just a 30 s snippet of programme to check.

No, I don't know how to get the get_iplayer GUI to do this. :-)

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Cheers, Ralph.
https://plus.google.com/+RalphCorderoy

YellowYeti

2017-11-06 19:00:52 UTC

Permalink

Post by Ralph Corderoy
I hadn't when he asked, but have since noticed it on last Thursday
night's _This Week_ downloaded on Friday. I adjusted the syncing
between the audio and video streams within the file to fix with
something like
ffmpeg -itsoffset 0.4 -i foo.mp4 -i foo.mp4 \
-map 0:1 -map 1:0 -c copy new-foo.mp4
IOW, have ffmpeg read the same file twice, taking the audio from one,
and the video from another, copying them into a new file, so no
transcoding, but with an "input time offset" applied to one of them of
0.4 s. The corrective delay is found through experimentation and adding
a `-to 00:00:30' after the `-c copy' helps that by quickly producing
just a 30 s snippet of programme to check.
No, I don't know how to get the get_iplayer GUI to do this. :-)

The 'old' recording of HIGNFY has the sound starting somewhere in the
middle of the continuity announcement before the programme itself starts.
The video starts with the programme titles. The 'new' recording, with no
offset, starts with the programme titles - i.e. the video is the same
for both recordings, it is the audio that is different.

Is there perhaps some automated up-loading that takes place by the beeb,
on a timed basis, which is eventually edited by someone to correct to
the start of the programme?

If that is the case, it may be possible to compare audio & video length
after downloading? My concern is that this appears to be something that
can happen at random times, and give random offsets - and means either
not using hq audio, or having to check each download.