PAL DVD Audio

[GParent]

I couldn't find an answer reading the FAQ or via a general search of the forum.

I am converting a PAL DVD to NTSC DVD:

SOURCE --> MPEG-2 25 fps PAL Interlaced

OUTPUT --> MPEG-2 29.97 fps NTSC Interlaced

I am converting video with this method: DVD2AVI --> TMPGEnc --> MPEG-2 NTSC


AUDIO QUESTION:

I am wondering if there is any need to convert the audio of a PAL DVD regards the Frame Rate. Can I just take the original 2-channel AC3 file from the PAL DVD and use it to re-author the NTSC DVD using the converted MPEG-2 file?

[tebasuna51]

If the output video duration is equal to source video duration, you can use the original AC3 audio.

[GParent]

I found the converted (TMPGEnc) MPEG-2 file (PAL -> NTSC) was 4 seconds less than the original AC3 audio file. I did a GOP timecode conversion and found the 4 second problem and had it fixed by DVD-Lab. Now, the video and audio are the exact same size and I am now compiling a DVD. Thanks for your reply.

The residual concern I have is what the relevancy, if any, does frame rate have to an audio stream that is paired with a video stream?

[tebasuna51]

Framerate is a clear concept for video because 1 frame = 1 picture.
Audio is continuous sound, then speak of framerate for audio have no sense; internally an ac3 is a succession of blocks (called also 'frames') of 32 ms (if 48 KHz.). If you want an ac3 have always (PAL, NTSC) a 'framerate' 31.25, and never is equal to standard video framerates.

Then an audio stream paired with a video stream only must have the same duration in time, framerate is always different.

[GParent]

I was able to mate the converted (PA --> NTSC) MPEG-2 stream with the original AC3 audio stream and the final DVD was perfect, regards no sync problems or delays.

However, I had to use DVD-Lab (great program) to re-write the timecode of the converted MPEG-2 file, otherwise there would have been 4 seconds difference in length with the audio.

I think I have a good formula now.

Thanks!

[Rafterman]

I've been trying a PAL to NTSC conversion using Procoder2 to do the Video file conversion to NTSC(using tmpgenc to simpley demux). However I cannot get the audio file to sync with the video file. I've been using Besweet(25000 > 239760 - AC3 to AC3) to convert the audio file without success. If I am reading your thread correctly are you saying you are not altering the audio file but using dvd-lab to make the converted NTSC video file the same length as the audio file?

[Matthew]

It is possible to take a deinterlaced 25 fps source, encode it at 720 x 480 25 fps, and then use DGPulldown to get to 29.97 fps (using flags). This will avoid a re-encode of the audio, without duplicating video.