Problem Extracting LPCM Audio from DVD

mnfesq · 27th April 2004, 01:06

I am making a back up of one of my DVDs. I successfully ripped the VOB and IFO files to my hard drive. I used DVD2SVCD to make an SVCD and the video came out fine but the audio was at high speed (like playing a 33 rpm record at 45 rpms) The video was 1 hr 6 mins 34 secs and the audio was 33.6 mins. For the second half of the video, there was no sound.

I manually ran dvd2avi and found that the audio was an LPCM stream. I had it convert to wav and came up with the same high-speed audio. The wav file was about 345 mb, and had a run time of 33.6 mins. I tried taking the wav file and, using Gold Wave, stretch it out to be 1:06:34. This worked actually, and I had a normal sounding wav that was the right time and was about 750 mb. The problem is, that it does not sync with the video and I am not aware of any way that I can fix that.

Why is the LPCM coming out so fast and is there anything I can do to fix this?

daphy · 27th April 2004, 07:42

try this: demux the sound again with f.e. smartripper
-> should be a WAV 16bit 48KHz with the complete playing time

post your results!

mnfesq · 28th April 2004, 00:50

No luck. Smartripper did not recognize the IFO file. DVD Audio Extractor didn't either. DVD Audio Ripper did, but it gave me the same 350 mb, 33.6 minute sped-up wav file that I got with DVD2AVI.

For what it is worth, i am backing up an old Marx Brothers movie, "Horsefeathers," and while it is a commercial DVD, it has a very basic structure, no menus, no extras and the LPCM audio track indicates how little space the entire vid takes up on the DVD.

If you have any ideas, they would be appreciated.

daphy · 28th April 2004, 06:40

you got the files stored on your hd? if not try tools like dvd shrink or nero to store them. I got a simular problem a year ago - after 'clean' storing the files I finally managed to work with them

mnfesq · 29th April 2004, 02:04

OK, I figured out the problem and was able to solve it. The problem was that the LPCM stream had a sampling rate of only 24 khz and dvd2avi and the other programs I tried extracted it to a wav file at 48 khz. That was why it sounded like it was being played back at high speed and why the time was cut in half.

I took the extracted wav file and, using Gold Wave, resampled it from 48 khz down to 24 khz. I ended up with a wav file that sounded perfect and was the same size as the originally extracted wav file. However, I couldn't use this file for an svcd video because 24 khz is not svcd-compliant and it gave me a really choppy video when i tried to mux it with my pulldown mpv. Therefore, I took the resampled wav and resampled it again, this time back up to 48 khz. I ended up with a 48 khz wav file that still sounded fine and had the right run time, but the file was twice the size.

I renamed the twice resampled wav file to give it the name that dvd2svcd gives to extracted wav files, re-processed it to mp2 with besweet (using dvd2svcd's recover function). Before I re-processed the audio file, I saved a copy of the d2s file for later use, then, after I had a good mp2 file, I restarted dvd2svcd, used the copied d2s file I had saved from before, and using the recovery function, restarted dvd2svcd at the muxing and cutting point. Everthing after that ran as usual and I ended up with a perfect svcd copy that had no sync errors.

What a pain in the backside this one was.

daphy · 29th April 2004, 08:19

Quote:

LPCM stream had a sampling rate of only 24 khz

I wouln´t know that this is possible because of the dvd-video specifications

mnfesq · 29th April 2004, 10:28

Quote:

Originally posted by daphy
I wouln´t know that this is possible because of the dvd-video specifications

I guess it was significant that I was backing up a copy of an old Marx Brothers movie. Because it was so old, the audio track is a single track mono stream. I guess most modern vids have at least two tracks with 24 khz per stream. I figured this out when I was doing some searches on google and came up with a spec sheet for LPCM that says that it can have a sample rate from 24 khz to 96 khz. I had assumed that all DVDs had a 48 khz sample rate.

27th April 2004, 01:06	#1 \| Link
mnfesq Registered User Join Date: Apr 2003 Location: Los Angeles Posts: 44	Problem Extracting LPCM Audio from DVD I am making a back up of one of my DVDs. I successfully ripped the VOB and IFO files to my hard drive. I used DVD2SVCD to make an SVCD and the video came out fine but the audio was at high speed (like playing a 33 rpm record at 45 rpms) The video was 1 hr 6 mins 34 secs and the audio was 33.6 mins. For the second half of the video, there was no sound. I manually ran dvd2avi and found that the audio was an LPCM stream. I had it convert to wav and came up with the same high-speed audio. The wav file was about 345 mb, and had a run time of 33.6 mins. I tried taking the wav file and, using Gold Wave, stretch it out to be 1:06:34. This worked actually, and I had a normal sounding wav that was the right time and was about 750 mb. The problem is, that it does not sync with the video and I am not aware of any way that I can fix that. Why is the LPCM coming out so fast and is there anything I can do to fix this? Last edited by mnfesq; 27th April 2004 at 01:09.

27th April 2004, 07:42	#2 \| Link
daphy Miles Freak Join Date: Apr 2003 Location: Europe Posts: 652	try this: demux the sound again with f.e. smartripper -> should be a WAV 16bit 48KHz with the complete playing time post your results! __________________ CYA Daphy

28th April 2004, 06:40	#4 \| Link
daphy Miles Freak Join Date: Apr 2003 Location: Europe Posts: 652	you got the files stored on your hd? if not try tools like dvd shrink or nero to store them. I got a simular problem a year ago - after 'clean' storing the files I finally managed to work with them __________________ CYA Daphy

28th April 2004, 00:50	#3 \| Link
mnfesq Registered User Join Date: Apr 2003 Location: Los Angeles Posts: 44	No luck. Smartripper did not recognize the IFO file. DVD Audio Extractor didn't either. DVD Audio Ripper did, but it gave me the same 350 mb, 33.6 minute sped-up wav file that I got with DVD2AVI. For what it is worth, i am backing up an old Marx Brothers movie, "Horsefeathers," and while it is a commercial DVD, it has a very basic structure, no menus, no extras and the LPCM audio track indicates how little space the entire vid takes up on the DVD. If you have any ideas, they would be appreciated.

29th April 2004, 02:04	#5 \| Link
mnfesq Registered User Join Date: Apr 2003 Location: Los Angeles Posts: 44	OK, I figured out the problem and was able to solve it. The problem was that the LPCM stream had a sampling rate of only 24 khz and dvd2avi and the other programs I tried extracted it to a wav file at 48 khz. That was why it sounded like it was being played back at high speed and why the time was cut in half. I took the extracted wav file and, using Gold Wave, resampled it from 48 khz down to 24 khz. I ended up with a wav file that sounded perfect and was the same size as the originally extracted wav file. However, I couldn't use this file for an svcd video because 24 khz is not svcd-compliant and it gave me a really choppy video when i tried to mux it with my pulldown mpv. Therefore, I took the resampled wav and resampled it again, this time back up to 48 khz. I ended up with a 48 khz wav file that still sounded fine and had the right run time, but the file was twice the size. I renamed the twice resampled wav file to give it the name that dvd2svcd gives to extracted wav files, re-processed it to mp2 with besweet (using dvd2svcd's recover function). Before I re-processed the audio file, I saved a copy of the d2s file for later use, then, after I had a good mp2 file, I restarted dvd2svcd, used the copied d2s file I had saved from before, and using the recovery function, restarted dvd2svcd at the muxing and cutting point. Everthing after that ran as usual and I ended up with a perfect svcd copy that had no sync errors. What a pain in the backside this one was.