Doing basic audio compression

[timmus]

I just tried rendering a DVD with home movies in this fashion:

Source files: M2V+WAV(pcm) -> TMpgEnc DVD Author

Unfortunately I tried fitting 4 hours of footage, producing a 17 GB master. I thought DVD Shrink could whack it down, but it will only take it down to 10.1 GB. OK, fine, I'll have to make a smaller movie.

The problem though -- the audio stream is 2.6 GB. I know the source streams are big, but evidently the authoring & shrink programs just encode them verbatim.

(1) Does this mean I have to go back to my source files and compress the WAV (pcm) audio stream?

(2) Can I just run Audacity or SoundForge on them and save them as something else? What is the danger of causing sync problems by doing this? What is the best format to save to in this situation?

I have heard recommendations to use AC3, but I'm not doing any Dolby channel type stuff.. is it still recommended?

[mats.hogberg]

(1) Yes.
(2) ...or ffmpeggui. I'd recommend AC3, yes, as it's universally accepted audio format for DVD. WAV/LPCM is the other, but is huge, as you've found out. MP2 is accepted by most players even if it's not required for NTSC players. I use tooLame for mp2 encoding.

/Mats

[yoda313]

but I'm not doing any Dolby channel type stuff.. is it still recommended

Just to expand on mats excellent suggestions Dolby is perfect for ANY audio use. Its ability for multichannel surround sound is well known. BUT you can do plain old stereo if you want. As mats mentioned AC3 is the default standard for dvds everywhere so thats a very good choice. However 99.9% of players out there will accept mp2 only dvds.

Just doing a 2.0 stereo ac3 should be just fine. If you want top quality you can use 448 bitrate or 384 should be more than adequate. Probably going lower than 224 is not a good idea.

[timmus]

OK, sounds good... I'll go back in and give it a shot with AC3.

However is there a danger of introducing sync problems? I want to get more info on this before I start redoing my source files.

[yoda313]

A program like ac3 cutter is supposed to be good at working out synch problems. Though its command line based and I haven't figured it out just yet.