MPEG-2: How should I convert PCM to AC3?

[webberm73]

Hi all. I need to know how is the best and/or most efficient way to convert the audio in my already encoded MPGs from PCM to AC3.

I have read that this conversion will cut down on the file size and will allow these shows to play in Dolby Digital on my JVC stand-alone.

I have encoded all my MPGs as DVD-compliant MPEG-2, 720x480, VBR @ approx. 3.5MBs with 48kHz audio.

Should I go ahead and do the conversion? Is it worth it? Each 10-12 minute episode is around 300KB in size and I am already able to squeeze 12-15 of these on a DVD-R. If I would gain enough room to fit another 2-3 episodes on the disc, I think it is worth the effort.

After researching, I'm thinking of demuxing the MPGs in TMPGEnc and then converting the audio stream to AC3 with Besweet and then remuxing the new streams together with TMPGEnc once again. Am I on the right track?

Any help/suggestions/corrections/remarks/obscenities are appreciated!

-Matt

[mats.hogberg]

I'm thinking of demuxing the MPGs in TMPGEnc and then converting the audio stream to AC3 with Besweet and then remuxing the new streams together with TMPGEnc once again. Am I on the right track?

Depending on the authoring package you use, there's no need to remux again - this is taken care of by the authoring package. Just demux and encode to AC3.

/Mats

[wulf109]

Instead of BeSweet try ffmpeggui,it's in the tools section,converts wav(pcm) to ac3 or mp2. Much easier to use and much better results.

[webberm73]

I tried both programs and like them both.

I must be lost somewhere in left field. I demuxed my MPG and got both the video and audio streams. The audio stream is MPEG Layer II. Should I convert this to WAV before encoding to AC3? I encoded the MPEG-2 audio to AC3 and there is no difference in file size. Have I missed something here?

Thanks in advance...

-Matt

[andkiich]

If the audio program will use the MPEG1-Layer2 audio then no, but a lot if not most will require the audio be in WAV format. In which case, you might want to check into VirtualDub Mod.

[duhmez]

besweet will transcode from mp2 to mp2. I do hear f issues with pioneer players from besweet ac3 though, which is indication of a depeer issue in besweet re: ac3.
ffmpeg isnt perfect for ac3 either. The world is still waiting for a perfect 100% compliant issue free, FREE ac3 encooder.

Personally, I do not have, nor wil I ever have, a pioneer dvd unit, so for me I pretty much stick to besweet.

[webberm73]

Thanks all for the generous help and advice.

The problem that I am having here is ME! I got my terminology and formats all screwed up in the beginning before I posted this and now I've fixed my own problem after some researching. By the way, mega-kudos to LordSmurf's web site for fantastic information!

Here's the story: I thought that the MPEGs that were encoded had PCM (WAV) audio in them. When I demuxed the MPEGs, I found there was MPEG-1 Layer 2 audio instead. When converting the MPEG-1 audio to AC3, I was expecting a file size decrease. I didn't. Since MPEG-1 Layer 2 audio is already compressed, switching the audio to AC3 just changed the format and the file size maintained the same size, plus/minus a few KB. In a nutshell, I thought MPEG-1 audio was PCM audio. This works out anyways, since I want to author my discs with AC3 anyway.

Hope this helps someone if they experience the same problem in the future.

Should I place more than one layer of audio on my DVD when I go to author it?

/MW

[mats.hogberg]

You can put more than one audio track on a DVD: MP2, LPCM WAV and AC3.
MP2 and AC3 at the same bit rate (of course) results in audio files of the same size (everything that has the same bit rate generates a file of the same size from a given input file). What differs is the quality at a given bit rate.
Not all players can handle MP2 audio, but all do handle AC3 and WAV. I suggest you try AC3 only. Some players are reported to only accept 5.1 (6 channel) audio as AC3, but you can encode a stereo wav to 5.1 AC3 with ffmpeg.

/Mats

[dun4cheap]

Question for the pros.

I am currently working on a large cheer DVD for my daughters cheer team. I have chosen Studio 8 for my editing and dvd authoring. Yes I know studio 8. Well the fact is even with its bugs it has a lot of unique features and the dvd authoring is very advanced compared to many others. My final product is almost complete, the menus run great the video is all in sync but I want AC3 audio which is not available in studio 8 but will be in studio 9. So is it possible to demux my vob files and then use besweat or another program to convert my audio to ac3 then remux my vobs, or does this have to be done at the mpg level. If this is the case then I will be stuck with mpg audio until studio 9 comes out. I choose video quaility over audio compatability, so this is why I have chosen mpg audio for now.

Thanks for any help.