audio delay correction

[fjhdavid]

Dear all,

I spoke about this feature to include in DVD-RB 3 or 4 months ago.

Is there a work on progress on this subject?

the purpose should be to allow an automatic audio delay correction that occure in many DVD (the delay sometimes increase as you go to the last VOB file)

in the same time time could it be possible to tweak the sound level with a "normalize button" or "a audio gain slider" for example?

thanks
francois

[Fishman0919]

This has been talked about before....

http://forum.doom9.org/showthread.php?t=112599&highlight=normalize+audio

http://forum.doom9.org/showthread.php?t=80172&highlight=normalize+audio

...as for the delay.... DVD-RB copies the org audio from the movie... so the delay should be the same as the org disc

[stereo]

I know almost nothing about this, but I read somewhere (where?) that the audio delay repported by this or that program is actually non-exsistent, and that, in fact, it is present (repported) only as a result of a flaw in the authoring package that was used.

I stipulate: I know almost nothing about this. This was just something I picked up somewhere.

[fjhdavid]

in fact, DGindex reported a wrong number in old version, but now the reported audiodelay is correct and sometimes up to 500ms

Rejig is able to correct the audio delay very easaly, but you have to do it after or before DVD-RB.

what I suggested some months ago, was just to add in DVD-RB two buttons: one for an automatic or a manual audiodelay correction and the other button in order to nomalize the audio chanel and increased the audio amplitude by a % factor

should it be easy to implement this very useful things?

an other way should be to allow the use of avisynth audio filters in DVD-RB.

thanks for your advice
Francois

Of course I own the pro version which is outstanding!

[Fishman0919]

hmmm. I think you are thinking of the audio delay as something bad.

The audio delay is set when arthoring the movie to correct an offset between the audio and video. If the audio delay is -33ms for a given movie... then it should be left at -33ms... meaning the audio is 33ms ahead of the video in timing and needs to be delayed by -33ms. If you change the audio delay and bring it to 0ms then the audio will no longer be in sync with the video and the sounds will not match the org disc.

When DGindex tells you the audio delay is -33ms... it mean the audio is out of timing by 33ms and needs to be delay -33ms when arthoring in other to stay in sync with the video.

DVD-RB re-encodes the video and puts the audio back the same way it was with the org disc... so the audio stay in sync just like with the org disc.

[fjhdavid]

my DVD are coming from a DVD recorder. I recorded film from my satellite box, and with dgindex I have up to 500ms audio delay and I can see it when I watch the movie.

so I need (but orhers here too), an audiodelay correction capabilty and if it could be implemented into DVD-RB, it would be wonderful

but as I said, it should be sufficient that DVD-RB allow the use of audio avisynth filter...

about the audio channel normalization or gain changing, you already watched (I am sure), movie with a very weak sound level.
but one more time it is possible to use avisynth filter.

it's up to dvd-rb author to choose the most efficient way to implement audio stuff.

[jdobbs]

my DVD are coming from a DVD recorder. I recorded film from my satellite box, and with dgindex I have up to 500ms audio delay and I can see it when I watch the movie.Thanks for this info. I was wondering how the sound on a commercial DVD could possibly need adjusting...

It would be easiest to adjust the value in DVD-RB rather than with an AVISYNTH filter. The audio isn't passed through today, and if it was, it would have to be reencoded to AC3 (or MPEG audio) and reintegrated. That would hold true for any audio volume adjustment as well (including normalization).

I'll look at the code and see how hard it would be to implement a delay callout. But, I don't think it'll be that hard, since I'd just have to adjust the existing timing information in each audio packet against a fixed value.

[Fishman0919]

my DVD are coming from a DVD recorder. I recorded film from my satellite box, and with dgindex I have up to 500ms audio delay and I can see it when I watch the movie.

ah... yes... I too just couldn't understand the need to adjust the audio of a commercial DVD.

fjhdavid, sorry about that... but that info could have been help in the beginning

[fjhdavid]

thank you for your reactivity! and this great piece of software

two additional info:

- for the audio Gain: I need an additional 6dB to 12dB (depending of the channel recorded and then the corresponding DVD)


- for the delay, the value is not the same all along the film
it is usually 64ms for the first VOB of 1GB
about 128ms for the second VOB of 1GB
256ms for the third....
and so on, up to 500ms for the fourth when the movie is more than three VOBs

sometimes it is only 384ms for the last VOB, but in general 400ms to 500ms is the typical delay for the 2hrs movie last VOB


PS: I have around 700 DVD recorded from my sat box and every one I tested exhibit this amount of audio delay and need for Gain correction

[jdobbs]

Wow... that gets complicated. It sounds more like a problem with your recorder. There's no reason why your audio should drift over time like that. Are you recording using a settop box, or a PC with some software? Also, how is your audio input to the recorder (digital of analog connectors -- I'm only aware of analog settop recorders).

Are you doing any kind of framerate conversions (PAL/NTSC) or IVTC as a part of your process?

[fjhdavid]

I am using a settop box with analog audio input to the recorder and I am not doing any kind of framerate conversions (PAL/NTSC) or IVTC as a part of my process

but If you allow to change the audio delay (automatically and manually), it should be ok.

if you allow also to change manually and automatically the audio gain, it should be also perfect!

[Fishman0919]

fjhdavid

What does DGIndex say the delay is if you load all the VOB's into in at the same time... not just 1

I just load Transformers into DGIndex... when I load all 7 VOB's in it show an audio delay of 0ms... what it should be... if I load each one on it's own they are all out of whack... -156ms, -244ms, -322ms.... -414ms

[fjhdavid]

it is the same for me, surprising...

If I fed dgindex with one big VOB (including the sum of vob 1 to 5) I have a small value (around -80ms) and If I fed dgindex with VOB from 2 to 5, the audio_delay is increasing...

in fact it is not double each time, the equation is more like this (and more like yours):

audio_delay_Vob_n+1 = audio_delay_vob_n+ 80ms

do you remebrer the systematic error of previous dgindex of -80ms (it forgot the two first frames If I remember)...maybe it hasn't been solve for VOB going from 2 to n...?

[elguaxo]

Thanks for this info. I was wondering how the sound on a commercial DVD could possibly need adjusting...

It would be easiest to adjust the value in DVD-RB rather than with an AVISYNTH filter. The audio isn't passed through today, and if it was, it would have to be reencoded to AC3 (or MPEG audio) and reintegrated. That would hold true for any audio volume adjustment as well (including normalization).

I'll look at the code and see how hard it would be to implement a delay callout. But, I don't think it'll be that hard, since I'd just have to adjust the existing timing information in each audio packet against a fixed value.

Any news about a manual 'audio delay'? Many Chinese/Hongkonese retail DVDs have audio problems that could be fixed with a delay.

Thanks!