LPCM?

[Sakuya]

I heard that LPCM can have up to 8 channels of audio? How is it different from Dolby Digital 5.1? I have this DVD that I want to buy and it lists their audio selections as LPCM and stereo. What's the difference between LPCM and stereo?

[redwudz]

Look in 'Glossary' under 'Linear PCM', also '5.1 Audio'. <<< You can have up to 8 channels but it takes up a lot of space. Differences between LPCM and stereo depend on the DVD.

[daphy]

LPCM with more than 2 channels is not part of the DVD-Video standard (afaik also not in NTSC land )
so LPCM means uncompressed stereo
-> the other 'stereo' could only be AC3 or MP2 ?!?

bye daphy

[dcsos]

LPCM and stereo
LPCM is similar to what you get on an audio cd

Its way superior to the other "LOSSY" compressed formats authorized to be used on DVDs (eg Dolby 2.0 or 5.1 or MPEG AUDIO)

[daphy]

LPCM is similar to what you get on an audio cd

yep the main diffrence is the sampling rate (the bit rate can be up to 24 bit):
AudioCD 44.1KHz
LPCM/AC3/DTS/MP2 on DVD-Video 48KHz

[Abond]

8 channels? Great!
Good luck to found something to play them :P

[drjtech]

LPCM up to 8 channels is part of the DVD Spec:

[3.6.2] Audio details of DVD-Video

Linear PCM is uncompressed (lossless) digital audio, the same format used on CDs and most studio masters. It can be sampled at 48 or 96 kHz with 16, 20, or 24 bits/sample. (Audio CD is limited to 44.1 kHz at 16 bits.) There can be from 1 to 8 channels. The maximum bit rate is 6.144 Mbps, which limits sample rates and bit sizes when there are 5 or more channels. It's generally felt that the 120 dB dynamic range of 20 bits combined with a frequency response of around 22,000 Hz from 48 kHz sampling is adequate for high-fidelity sound reproduction. However, additional bits and higher sampling rates are useful in audiophile applications, studio work, noise shaping, advanced digital processing, and three-dimensional sound field reproduction. DVD players are required to support all the variations of LPCM, but many subsample 96 kHz down to 48 kHz, and some may not use all 20 or 24 bits. The signal provided on the digital output for external digital-to-analog converters may be limited to less than 96 kHz and less than 24 bits.

Here's some info on authoring and playing back a DVD with 8 channel LPCM:
Authoring multi-channel LPCM on DVD's

-drj

[Sakuya]

If I want to take the DVD with the LPCM audio and reauthor onto a new DVD and if I want to add more episodes to that new DVD, I'll have to change the LPCM audio to AC3 in order to have more space, right?

Can I just use ffmpegGUI to convert LPCM to AC3? What bitrate should I select?

[Cornucopia]

If I want to take the DVD with the LPCM audio and reauthor onto a new DVD and if I want to add more episodes to that new DVD, I'll have to change the LPCM audio to AC3 in order to have more space, right?

Can I just use ffmpegGUI to convert LPCM to AC3? What bitrate should I select?

Yes, change to AC3 or MP2

Bitrate should be what allows your desired length to fit the disc (use a bitrate calc). Common rates are 224, 192kbps (for stereo streams). ffmpegGUI should allow you to do that (don't know, haven't had need to use it).

Scott

[Sakuya]

I've always used 384 as bitrate. I'm not sure why but that's what I always chose. Does it make the audio nicer or what's the difference between bitrates?

[edDV]

8 channels of LPCM could be accessed 2 at a time (4 stereo language tracks, or 4 angles with separate stereo audio, etc.) but would consume over half the DVD bitrate leaving room for only low quality video.

That is why MP2 and AC-3 compression are used.