48/16 Lossless audio vs 768kbps AAC

[nateo200]

So I've been wondering for a while how does 48/16 Lossless audio encoded to 768kbps AAC sound compared to the original? Has anyone done a good test with this? I always here 320kbps AAC is transparent to AC3 at the same bit rate if I had a 5.1 48khz 16bit DTS-Master/TrueHD/PCM/FLAC file and transcoded it to 5.1 AAC at 768kbps VBR how much quality is retained?

AAC from the God only knows how long Ive been encoding with it for basic portable devices is very efficient at bit rates very low but with lossless audio I have sort of become a stickler about making sure I keep a very high quality and a portable sized audio file for all my Blu-ray rips.

Really curious to see some tests done on this. I have a 7.1 AVR but my speakers are not up to audio file grade...

[Blue_MiSfit]

Only you can decide this for yourself. Do some test encodes.

Somebody might tell you that 320kbps AAC is totally transparent to a DTS-MA source, but you might not agree with that.

Derek

[nateo200]

Originally Posted by Blue_MiSfit

Only you can decide this for yourself. Do some test encodes.

Somebody might tell you that 320kbps AAC is totally transparent to a DTS-MA source, but you might not agree with that.

Derek

Alright I guess I gotta get to work! No problem with that! I'm going to do a blind test with a bunch of people, including some self proclaimed "experts" don't even know what PCM is!

Any suggestions on 5.1 lossless movies with parts that could be used for the test? Obviously I don't want them assuming that the "louder" track of an action movie is superior based on volume alone! :O

I have Super 8, The Expendables, and Crank ripped thus far and no BD reader to rip others...looks like the first two are 7.1 and the last is 6.1 (well faux 7.1 in that the rear surrounds are mono :O)...all lossless but I guess a 5.1 down mix won't matter so long as I down mix to 5.1 on both lossless and lossy AAC.

[turab]

Blue_MiSfit is right, but bear in mind that most people encode somewhere between 320kbps and 448kbps because that's what they find to be transparent, so the chances of even needing 768kbps are really really slim. As for what samples to test, I would go for a variety with different frequencies. Your judgement won't be good if you just listen to speech.

If I were to recommend a "safe" bitrate, it would be ~448kbps. (If you can notice artefacts, then of course go higher.) Also, there are some codecs that can target perceptual quality rather than bitrate. Have you considered that? You'll find that different audio sources have different bitrates when you target quality. It might be more sensible to go that route.

[Atak_Snajpera]

I think it would be easier to just focus on 2.0 (stereo). Personally I can not notice difference between CD (FLAC) and Fraunhofer AAC at 128kbps on decent headphones. if 64kbps for one channel is enough so 320kbps should be also sufficient for 5.1 (5 * 64 kbps = 320kbps. LFE is very easy to compress therefore we don't count it)

[ramicio]

Encode that 5.1 DTS-HD Master track right to FLAC and see what bit rate you end up with. You might be surprised how low it is. With today's cheap storage, lossy is a waste for anything other than a portable device, because they are still frustratingly small in storage.

[nateo200]

Originally Posted by ramicio

Encode that 5.1 DTS-HD Master track right to FLAC and see what bit rate you end up with. You might be surprised how low it is. With today's cheap storage, lossy is a waste for anything other than a portable device, because they are still frustratingly small in storage.

I've been surprised at the bit rate as I have already done this! FLAC has better compression than both TrueHD and DTS-MA (I ran my own test with the appropriate encoders on my MacBook pro).

Even when TrueHD has no core FLAC can go lower...I almost think it should be in the Blu-ray spec but thus far Akira and few concerts are really only where compression is important, Akira was 192khz/24bit 6ch...and took over half the BD50 disc and they had Dolby Laboratories custom design the encode and get the AC3 core down to 128kbps to fit the damn thing on the disc (thats just an example of insane compression). I think DTS-MA's core is a downfall even if it provides backwards compatibility a static bit rate to me in this age just seams terribly inefficient. Surely a dead quiet scene does not need 1510kbps (assuming full bit rate DTS).

Originally Posted by turab

Blue_MiSfit is right, but bear in mind that most people encode somewhere between 320kbps and 448kbps because that's what they find to be transparent, so the chances of even needing 768kbps are really really slim. As for what samples to test, I would go for a variety with different frequencies. Your judgement won't be good if you just listen to speech.

If I were to recommend a "safe" bitrate, it would be ~448kbps. (If you can notice artefacts, then of course go higher.) Also, there are some codecs that can target perceptual quality rather than bitrate. Have you considered that? You'll find that different audio sources have different bitrates when you target quality. It might be more sensible to go that route.

Yeah for speech HE-AAC at 32kbps 32khz/16khz sounds fine....no denying that. I'm talking about how AAC would compare to industry lossless formats at bit rate X. I've encoded enough stuff to know what bit rate I think is fine but I couldn't help but wonder what would be considered essentially lossless. I read some stuff about some contests on who could create the best compression with the lowest size and good quality with video, audio and files...pretty cool stuff. But I made the thread about bit rate but I know plenty about perceptual quality, HE-AAC has just literally spun my world around, Ive never seen such amazing quality at such low bit rates! My Blu-ray rips usually include an HE-AAC track and a lossless FLAC/TrueHD/DTS track.

[ramicio]

Most of the time when I encode a 5.1 DTS-HD Master file that is 16 bits to FLAC, it winds up being even smaller than the lossy 1,509.75 kbps core! 24/192 in 5.1 channels seems like a total waste of space. If I was ripping that for storage I would just go down to 24/48.

[turab]

Originally Posted by nateo200

Yeah for speech HE-AAC at 32kbps 32khz/16khz sounds fine....no denying that. I'm talking about how AAC would compare to industry lossless formats at bit rate X. I've encoded enough stuff to know what bit rate I think is fine but I couldn't help but wonder what would be considered essentially lossless. I read some stuff about some contests on who could create the best compression with the lowest size and good quality with video, audio and files...pretty cool stuff. But I made the thread about bit rate but I know plenty about perceptual quality, HE-AAC has just literally spun my world around, Ive never seen such amazing quality at such low bit rates! My Blu-ray rips usually include an HE-AAC track and a lossless FLAC/TrueHD/DTS track.

I brought up perceptual quality because different sources will produce different bitrates if you're targeting constant quality (which you are). Therefore, besides this being dependant on the listener and the equipment used, there is no real answer.

For high bitrates, I think AAC LC is more appropriate. HE-AAC introduces additional compression techniques such as spectral band replication and parametric stereo (my source being wikipedia ) which help at low bitrates, but do more harm at the sort of bitrates you want.

[nateo200]

Originally Posted by turab

I brought up perceptual quality because different sources will produce different bitrates if you're targeting constant quality (which you are). Therefore, besides this being dependant on the listener and the equipment used, there is no real answer.

For high bitrates, I think AAC LC is more appropriate. HE-AAC introduces additional compression techniques such as spectral band replication and parametric stereo (my source being wikipedia ) which help at low bitrates, but do more harm at the sort of bitrates you want.

Agreed 100%. I've been using HE-AAC simply because I almost don't want a lossy track taking up anymore space and these HE-AAC tracks are like 35-70 megabytes so they are so small. I use AAC LC when I have a simple AC3 track and need another solid lossy track for mobile devices (though I am increasingly not playing movies on mobile devices as I find my laptop with me everywhere ).

Originally Posted by ramicio

Most of the time when I encode a 5.1 DTS-HD Master file that is 16 bits to FLAC, it winds up being even smaller than the lossy 1,509.75 kbps core! 24/192 in 5.1 channels seems like a total waste of space. If I was ripping that for storage I would just go down to 24/48.

Well Akira was sort of an Audiophile project by the maker of it. He recorded all the audio in analog on the highest fidelity analog tape at the time (which technically has no real sample rate) so when he did the transfer he wanted the best digital quality possible (he originally wanted a 5.1 LPCM 192khz/24bit mix :O) based on a theory of supersonic frequencies stimulating the brain despite not being audible...not sure how I feel about it but interesting. But yeah I use Handbrake for most everything which only encodes FLAC at 48/16 but 24bit is nice but not always needed. But sometimes if I have a TrueHD mix its very small as well...like I ripped Super 8 which was TrueHD 7.1 24bit and it was only about 2.3gigs...I think MLP/TrueHD is a better codec for getting the smallest file but Master Audio offering the best compatibility and FLAC good for storage...just my views though.

[Blue_MiSfit]

In these discussions it's worth mentioning the method of transport to your amplifier. I usually go with AC3, because I use S/PDIF to connect my computer to my receiver, which means AC3 or DTS are my best options for multichannel audio.

AAC is great, but my receiver doesn't support it - which means I have to transcode to AC3 on the fly if I want to transport 5.1 channels over S/PDIF. For 2 channel, I can do 24/96 PCM, but surround has its own challenges. HDMI has tons more bandwidth but brings its own annoyances...