AC3 5.1 to LPCM 5.1 possible?

[Socio]

Hello,

I am testing upscaling DVD to Blu Ray and was thinking that since I would have the room it may be advantageous to convert AC3 to LPCM, with the idea that LPCM would be uncompressed thus theoretically better sound quality.

I sure would like to test this so is there away to convert AC3 5.1 to LPCM 5.1?

Thanks

[tebasuna51]

Of course, is possible, but the LPCM quality is the same than the source. You can't obtain better quality.

[jamos]

The one big advantage of converting to lpcm is streaming to devices that do not support the audio format that the original video was in. Such as True-hd on the ps3...etc. but as stated above the quality does not increase.

[Socio]

The one big advantage of converting to lpcm is streaming to devices that do not support the audio format that the original video was in. Such as True-hd on the ps3...etc. but as stated above the quality does not increase.

Yes there is the streaming via HDMI aspect plus you can up it to 7.1 LPCM!

Now I am not sure of the best approach for this but this is what I tried so far;

I found I could convert the demuxed AC3 to 6 channel .wav with Besweet/Belight. Then I used a little program called DbPoweramp Music Converter with its Channel Split plugin to split the 6 channel .wav in to six mono .wavs.

Next I used Nero SoundTrax to make the split surround left and right in to a stereo .wav. Then I used the V.I Stereo to 5.1with Foobar guide with that stereo .wav to make a 5.1.wav.

I then I used DbPoweramp Music Converter with its Channel Split plugin to split that .wav

I fired up Nero SoundTrax again and created a 7.1 .wav using discrete channels; I used the FL, FR, C, LFE , SL and SR from the original .wav split for the first six channels and the BL and BR from the V.I Stereo to 5.1with Foobar .wav split for the rears.

Exported it as a 7.1 .wav file, used TsmuxeR to mux it for Blu Ray with my upscaled X264 DVD test clip and it makes it LPCM.

It sounds pretty good I also tried just using the Nero SoundTrax Surround expansion filter on a copy of the SL and SR to create rears which was not bad, I tried the surround reverb filter as well and it makes it kind of garbled.

If anyone knows of a better way to mix rears for 7.1 I sure would like to know.

[Socio]

For the curious;

I found an even better solution I did as above except I used the Foobar foo_dsp_fsurround plug-in to create the 5.1 mix instead of V.I.

The foo_dsp_fsurround plug-in makes a Dolby Pro Logic II type surround channel mix and it seems to blend very well with the existing 5.1 sound for creating bitstreamable 7.1 LPCM from a 5.1 ac3.

Edit: Upon further testing with foo_dsp_fsurround plug-in I found that I get a lot odd distortions so it might not be the way to go.

[jamos]

Yes there is the streaming via HDMI aspect plus you can up it to 7.1 LPCM!

Now I am not sure of the best approach for this but this is what I tried so far;

I found I could convert the demuxed AC3 to 6 channel .wav with Besweet/Belight. Then I used a little program called DbPoweramp Music Converter with its Channel Split plugin to split the 6 channel .wav in to six mono .wavs.

Next I used Nero SoundTrax to make the split surround left and right in to a stereo .wav. Then I used the V.I Stereo to 5.1with Foobar guide with that stereo .wav to make a 5.1.wav.

I then I used DbPoweramp Music Converter with its Channel Split plugin to split that .wav

I fired up Nero SoundTrax again and created a 7.1 .wav using discrete channels; I used the FL, FR, C, LFE , SL and SR from the original .wav split for the first six channels and the BL and BR from the V.I Stereo to 5.1with Foobar .wav split for the rears.

Exported it as a 7.1 .wav file, used TsmuxeR to mux it for Blu Ray with my upscaled X264 DVD test clip and it makes it LPCM.

It sounds pretty good I also tried just using the Nero SoundTrax Surround expansion filter on a copy of the SL and SR to create rears which was not bad, I tried the surround reverb filter as well and it makes it kind of garbled.

If anyone knows of a better way to mix rears for 7.1 I sure would like to know.

eac3to will do all what you need easier than what you are doing. just export it to pcm, run pcm2tsmu on the pcm file then mux it with tsmuxer.

[Audionut]

Yes there is the streaming via HDMI aspect plus you can up it to 7.1 LPCM!

Stay true to the source.

You are not gaining any quality by encoding to PCM.

AC3 is support by tons of devices these days. I would just stick to the original file.

What your attempting to do is destroy the original audio that the director intended you to hear by adding fake channels.
Then increase it's size 100x.

[Socio]

Stay true to the source.

You are not by encoding to PCM.

AC3 is support by tons of devices these days. I would just stick to the original file.

What your attempting to do is destroy the original audio that the director intended you to hear by adding fake channels.
Then increase it's size 100x.

I agree, gaining any quality by decompressing it theoretical at best.

However I believe you can stay true to the source and still enhance it.

Ideally what I want to do is take the left and right surround and extract the difference between the two. That difference would make a surround rear center or 6.1 without altering the original source or intended surround sound field.

Then extract the difference between the left surround and newly created center rear surround for the left rear surround and extract the difference between the difference right surround and the center rear surround for the right rear surround.

This would give me stereo left and right rear surrounds; these would be real not fake channels because you would simply be extending the original surround field again without altering the original source or intended surround sound field.

However I am still looking for a software solution to accurately extract the difference between stereo sources. It seems what I have tried so far is geared toward extracting vocals from a stereo source for the center output which is useless for what I want to achieve.

I also know they will be large audio files but since I will be burning to Blu Ray I will have sufficient room and be able to stream LPCM 7.1 through HDMI which is a plus.

[Audionut]

I agree, gaining any quality by decompressing it theoretical at best.

No. I never even mentioned "theoretical". The information that the AC3 encoder has turfed is gone for good. You won't get any of that back by encoding to PCM or any other thing.


However I believe you can stay true to the source and still enhance it.

That's like saying you can paint an apple yellow and still call it a red one.


Ideally what I want to do is take the left and right surround and extract the difference between the two.

Then extract the difference between the left surround and newly created center rear surround

There would be virtually no information left in your "newly created left and right rear surrounds".

[Socio]

No. I never even mentioned "theoretical". The information that the AC3 encoder has turfed is gone for good. You won't get any of that back by encoding to PCM or any other thing.




That's like saying you can paint an apple yellow and still call it a red one.




There would be virtually no information left in your "newly created left and right rear surrounds".

Not necessarily;

I did a simple test, I took the original left and right surround mono’s and made them a single stereo wav. I used Foobar and the Foobar channel mixer plugin, enabled surround sound and made a 5.1 wav from that stereo wav.

I split that 5.1 in to mono wav files and took the center channel from it and made two stereo wavs one with the center and the original left surround and one with the center and the original right surround.

I again used Foobar and the Foobar channel mixer plugin to make 5.1 wav’s from each and spit them both and took the center channel from both the splits and used them as the left and right rear surrounds.

"Both retained ample information".

The only thing I am not sure about is how the foobar channel mixer matrixes the center, a mix of both or the difference between both.

I am also not sure this it actually the ideal approach for achieving this either.

[Blue_MiSfit]

Why bother with all this? Just save time and space, stream the AC3 to your receiver through HDMI, and let it do the expansion to 7.1ch itself. It will do just as well if not better, and it will do it all on-the-fly.

You're not gaining anything!

~MiSfit