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Old 08-09-2008, 07:43 PM   #1
hokoall
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Default EDIUS: Video/audio sync problem when using VBR

Hello

I am using Edius 'DVD Creator' to produce DVDs (or at least output files for later burning). All is well when I use constant bit rate video, however, there is a sync problem between video and audio that gets worse towards the end of the DVD whenever I switch to variable bit rate video.

In both cases I have restricted the overall bitrate (video and audio) to less than 8 Mbps.

Some technical details:
- using EDIUS 4.61;
- overall length of timeline: 2:27:00 h;
- CBR test: 3.7 Mbps video rate, 256 kbps audio rate (AC3);
- VBR test: maximum 7.6 Mbps video rate, 384 kbps audio rate (AC3);
- viewing DVD files using 'MediaPlayer Classic' (a great open-source media player available from here: http://www.afterdawn.com/software/vi...9_1__20080127_).

Looking at the temporary 4.5 GB mpg file generated in the DVD_Temp folder (together with the IFO and VOB files in the VIDEO_TS folder) I note that there is no sync problem whatever video bit rate type I use. So where is the problem ? I expected where video and audio are contained in the same VOB file there should be no possibility for sync problems.

As the timeline is more than 2 h long I'd much rather use VBR and CBR as the image quality appears very slightly better when using VBR.

Any advice much appreciated,
hokoall
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Old 08-09-2008, 10:15 PM   #2
Ron Evans
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What is the audio source on the timeline? Is it 48k WAV? IF it is anything else it could be the source of your problem especially mp3.

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Old 08-10-2008, 09:33 AM   #3
hokoall
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Quote:
Originally Posted by Ron Evans View Post
What is the audio source on the timeline? Is it 48k WAV? IF it is anything else it could be the source of your problem especially mp3.
Hello Ron, thanks for your comment.
Yes, the audio source is 48 kHz PCM WAV (as captured together with video).

What I still don't understand though is how video and audio are in sync in the temporary mpg file which, I believe, is the source for the DVD-VOB files where they are out of sync when using VBR but in sync when using CBR.

For the current project I will stick with CBR as this works fine (just), but for future work I would really like to find out where this problem comes from. So I am curious to hear from all those other experts out there.

As an aside on data rates, it crossed my mind that encoding for DVD at a video rate of 3.7 Mbps is actually above the total data rate of a standard compressed DV signal (3.4 Mbps, correct me if I am wrong). Therefore, as long as using DV source material I reckon that there should be no significant improvement in image quality if I were to use a higher data rate (e.g. when using VBR or encoding for a double-layer DVD at 7.7 Mbps).
Any views on this one ?

hokoall
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Old 08-10-2008, 02:53 PM   #4
Ron Evans
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Quote:
Originally Posted by hokoall View Post

As an aside on data rates, it crossed my mind that encoding for DVD at a video rate of 3.7 Mbps is actually above the total data rate of a standard compressed DV signal (3.4 Mbps, correct me if I am wrong).

hokoall
DV is 25Mbps or about 3.4MBps so about 3 times compression for DVD, is intra frame rather than inter frame 15 GOP too, so is much higher quality than can be achieved with mpg encoding at this data rate. My projects are usually over 2 hours too and though I would normally use TMPGenc to encode have used DVD Creator in Edius with no problems using VBR and making the disc about 90% full. I don't like to use more than 4G of DVD disc to avoid edge defects and for max compatibility.
What do you use to burn DVD and have you tried using the Temp mpg file in another authoring program, have you let Edius Creator burn a disc?

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Old 08-11-2008, 07:34 PM   #5
hokoall
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Hello again

Quote:
Originally Posted by Ron Evans View Post
DV is 25Mbps or about 3.4MBps so about 3 times compression for DVD,
Oops, I knew there was something wrong, bits and Bytes... oh dear. :))


Quote:
Originally Posted by Ron Evans View Post
My projects are usually over 2 hours too and though I would normally use TMPGenc to encode have used DVD Creator in Edius with no problems using VBR and making the disc about 90% full. I don't like to use more than 4G of DVD disc to avoid edge defects and for max compatibility.
What do you use to burn DVD and have you tried using the Temp mpg file in another authoring program, have you let Edius Creator burn a disc?
The burning doesn't come into it as I am using MediaPlayerClassic to "play the DVD" off the files in the VIDEO_TS folder created by 'DVD Creator'. (If I couldn't do that I would have ended up with a pile of scrap disks by now.)
Of course, it could mean that MPC is making a mess of the VBR playback, but I would expect that it puts out the data it finds inside the VOB files "bit by bit". Thus, if there is a timing difference between video and audio I'd expect that to have been introduced when the VOB file was created.

By the way, it is the video lagging the audio (in case this detail gives any clues to the potential source of the problem).

Getting back to your question: I have so far only used 'DVD Creator' as this project consists of 24 chapters with a contents menu. The only other bit of software I have to hand that could make (much more basic) DVD menus comes with Ashampoo Burning Studio 7. Because of its rather basic features I have not tried to use it for this one.

However, I am now using Ashampoo trying to burn a DVD(-RW) from the temporary mpg file. I'll be back with the results later.

hokoall
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Old 08-11-2008, 11:44 PM   #6
Ron Evans
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Until you actually burn a disc you can't really tell whether its the files or the playback program( which is likely the problem). Do you have another playback program? Do you have Nero to burn with? Or any burning program that will burn a DVD compliant disc.

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Old 08-12-2008, 07:30 PM   #7
hokoall
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Hello

Quote:
Originally Posted by Ron Evans View Post
Until you actually burn a disc you can't really tell whether its the files or the playback program( which is likely the problem). Do you have another playback program? Do you have Nero to burn with? Or any burning program that will burn a DVD compliant disc.
I don't have another program at present that will play back plain VOB files, so no much luck on this front. And I also don't have any DVD-writer software other than Ashampoo (the rather ancient copy of Nero I got kicking about somewhere won't do DVDs).

The test to burn a DVD from that mpg file failed miserably as Ashampoo somehow choked after an hour or so and failed to complete the task.
I am now trying something else, converting the mpg file to VOB's using ProCoderExpress for EDIUS. However, I am not quite sure if that isn't actually what is under the bonnet of 'DVD Creator', so the results may be exactly the same. We'll see.

Aside of all this later this week I'll be away on holiday for a wee while, so don't expect much more from me for a while. But I will get back to this sooner or later. Thanks very much for the comments and suggestions so far.

hokoall
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