Audio Problems

[macuser1960]

I've downloaded an MPEG file but i tried everything to convert it to DVD.
It seems that the Audio is a little weird.

There were messages on the board where i've found it that some people had the same problems.
The guy says it plays with sound in PowerDVD, wich is for XP i assume.
With all my MAC programs i can not get the sound.

I've included a stucture of the file which i got from MPEG Streamclip.
Do you have a way to convert this to DVD?
The picture is not the problem, it's the AC3 sound, it has a lot of channels?.

Thanks in advance, Bert


Type: MPEG program stream

Duration: 0:03:41
Data Size: 331.98 MB
Bit Rate: 12.58 Mbps

Video Tracks:
224 MPEG-2, 1280 × 720, 16:9, 59.94 fps, 13.00 Mbps, progressive

Audio Tracks:
129 AC3 3/2, 48 kHz, 384 kbps
131 AC3 3/2, 48 kHz, 384 kbps
132 AC3 3/2, 48 kHz, 384 kbps
136 AC3 3/2, 48 kHz, 384 kbps
138 AC3 3/2, 48 kHz, 384 kbps
139 AC3 3/2, 48 kHz, 384 kbps
143 AC3 3/2, 48 kHz, 384 kbps
267 AC3 3/2, 48 kHz, 384 kbps

Stream Files:
Christina Aguilera-DCNYRE 2007 Candyman.mpg (331.98 MB)

[Case]

Get bbDEMUX to demux the streams. If you get one .m2v file and one .ac3 file, then MPEG Streamclip had trouble identifying the audio track in this file.
You can then re-mux the .m2v and .ac3 by naming the streams the same before the dot, then opening the .m2v in MPEG Streamclip (it will notice the .ac3 on its own because of the name) and Convert to MPEG. Check if the resulting file is approximately the same size as the original file. Also check if the video and audio are in sync: if there was an offset in the original file, then that would be lost after re-muxing.

[macuser1960]

Thanks Case,

You're the best.....

It works....

[macuser1960]

Hello Case,

Thought it worked, but the audio is a little out of sync.
Is there a program to fix that?

[Case]

While playing in VLC, you can delay the audio up and down by using the 'f' and 'g' keys, in steps of 50 milliseconds.
When it syncs, note down the value, e.g. "-200".
The plus/minus sign is reversed from the value used in ffmpegX, if I remember correctly, so "-200" in VLC is "200" in ffmpegX.
Then use that value in the Sync field in the Options tab when converting to DVD.

If you still have the converted ffmpegX output .m2v and .ac3 files, then you may use the Mux tool, which also has a Sync field.

[macuser1960]

I've just tried your sync option.
With VLC i needed -150 Ms to get it in sync.
I coverted the files again, reverted the number to 150.
It's still out of sync so now i'm trying with -150 and see what it does.
Hope this works, these HDTV files drive me up the wall.
Will let you know if it works.

[macuser1960]

I have tried but is keep's getting out of sync.
Will look for another file of it.

Thanx anyway, Case

[tomlee59]

By "keeps getting out of sync," do you mean that you are able to get good sync at, say, the beginning, but it drifts out of sync as the movie progresses? If the sync error is a constant amount, then the muxing offset method that Case described will fix it for sure.

Also, be sure to reset VLC's sync correction to zero. Otherwise, you might be verifying sync with a player that introduces an error!

If, on the other hand, the sync error changes over the length of the movie, then you have extra work to do. If the sync drifts at a constant rate, then you can use a tool such as Audacity (free) to change the duration of the audio track to match. The "change tempo" option in Audacity is perfect for this purpose.

If the sync error behaves in a more complex way, you may have to chop the movie into pieces, sync each separately, then recombine.

[macuser1960]

My audio stays out of sync.
It seems my audio is one second longer then my video.
Can i cut off 1 second of my audio with Audacity?

[tomlee59]

My audio stays out of sync.
It seems my audio is one second longer then my video.
Can i cut off 1 second of my audio with Audacity?

The important part is not so much whether it's out of sync (that's already understood to be the problem), but specifically how the sync error behaves. So, again, I ask: Is the sync error a fixed amount, or does it drift?

If the error is fixed, then remuxing with a constant compensation value will solve your problem.

If the sync error drifts at a constant rate (e.g., it grows as the movie progresses), then rescaling (not simply "cutting off") the duration of the audio track will fix that. As I stated in my previous post, use Audacity's "tempo change" tool to do this. To use it properly, you need to characterize the sync error at the beginning and end of the movie. Under the assumption of a truly fixed drift rate, those two data points (plus knowledge of the duration of the uncorrected audio track, which Audacity will also helpfully report) suffice to tell you what offset (if any) and duration adjustment needs to be made.