is there a difference between lossy and lossless bluray audio? - AVS Forum
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post #1 of 23 Old 06-22-2013, 02:52 PM - Thread Starter
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I'm about to upgrade to a yamaha avr avr with 7.1 support even though i have a 5.1 setup.
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post #2 of 23 Old 06-22-2013, 03:09 PM
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yes, there is a difference - "lossy" digital audio is compressed, lossless is not. HDMI digital audio like Dolby TrueHD will be uncompressed and "can be" more dynamic, clearer, with better channel separation. I used the term "can be" because your electronics, speakers, room setup and acoustics all effect the perceived quality of the sound. Many folks cannot tell the difference, some can spot the higher quality Dolby TrueHD or DTS-HD setup immediately compared to the older Dolby Digital coding. Also the audio coding on many Blu-ray disks can vary tremendously, depending on the effort put in by the Blu-ray publisher and the original audio for the movie.

I think for most home setups, the convenience of a single HDMI cable for both video and audio is worth the upgrade and if you actually hear an improvement with digital TrueHD or DTS-HD off your Blu-ray player, that is a bonus.
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post #3 of 23 Old 06-22-2013, 03:28 PM
 
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if you have a very high end system you will probably be able to tell the difference between DTS HD/Dolby TrueHD versus dolby and dts normal, but I would bet a large majority of systems couldn't
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post #4 of 23 Old 06-22-2013, 04:51 PM
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Quote:
Originally Posted by m_vanmeter View Post

yes, there is a difference - "lossy" digital audio is compressed, lossless is not.
Both lossy and lossless codecs are compressed. That's the whole point actually. They remove some of the data during the encoding process to save space and put the data back in the decoding step. Here's the difference: The lossy codecs use so much compression that some of the original data cannot be restored while the lossless ones use less compression and all of the data is restored.

Does this matter in terms of audio quality? Not likely, regardless of the equipment being used. Lossy outputs are not all the same. DVDs use relatively low bitrates while the lossy versions on Blu-ray use higher rates. They sound great, rivaling lossless in quality. So, if you are considering a new AVR just to get lossless decoding, it's probably not worth it. However, other features of a modern receiver such as improved room correction can make a difference.
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if you have a very high end system you will probably be able to tell the difference between DTS HD and Dolby TrueHD, but I would bet a large majority of systems couldn't
He is not asking about the difference between TrueHD and dts-MA. Beside, there isn't any difference - can't be since they both output PCM that is bit for bit identical to the original soundtrack fed into the encoder.
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post #5 of 23 Old 06-22-2013, 10:39 PM
 
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Originally Posted by BIslander View Post

Both lossy and lossless codecs are compressed. That's the whole point actually. They remove some of the data during the encoding process to save space and put the data back in the decoding step. Here's the difference: The lossy codecs use so much compression that some of the original data cannot be restored while the lossless ones use less compression and all of the data is restored.

Does this matter in terms of audio quality? Not likely, regardless of the equipment being used. Lossy outputs are not all the same. DVDs use relatively low bitrates while the lossy versions on Blu-ray use higher rates. They sound great, rivaling lossless in quality. So, if you are considering a new AVR just to get lossless decoding, it's probably not worth it. However, other features of a modern receiver such as improved room correction can make a difference.
He is not asking about the difference between TrueHD and dts-MA. Beside, there isn't any difference - can't be since they both output PCM that is bit for bit identical to the original soundtrack fed into the encoder.

I meant its very hard to tell the difference between TrueHD and dolby digital and DTS-MA and DTS on a system that isn't very high end as the difference isn't that much because blu-rays have pretty high bitrate dts/dolby tracks.
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post #6 of 23 Old 06-22-2013, 10:50 PM
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Thanks for clarifying. I think the evidence suggests it's hard, maybe not even possible, on any system.
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post #7 of 23 Old 06-23-2013, 07:38 AM
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Quote:
Originally Posted by BIslander View Post

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Originally Posted by m_vanmeter View Post

yes, there is a difference - "lossy" digital audio is compressed, lossless is not.
Both lossy and lossless codecs are compressed. That's the whole point actually. They remove some of the data during the encoding process to save space and put the data back in the decoding step. Here's the difference: The lossy codecs use so much compression that some of the original data cannot be restored while the lossless ones use less compression and all of the data is restored.

Exactly. As pointed out above there are two kinds of compression - lossless compression which is usually limited to about 1/3 to 1/2, and lossy compression which can, at a variable cost in sound quality, range up to 20:1 ( reduction of file size to 5 % or less). What may not be obvious is that various schemes for lossy compression and various kinds of music can produce differing results. Some place around 10:1 audible degradation can become very noticable, but that partially depends on the musical work and the exact compression algorithm.

Lossless compression can produce ideal and perfect reconstruction of the source music file.

There are far more different lossy compression schemes than lossy decompression or reconstitution schemes. A file can be compressed using one of 10 different schemes but decompressed using just one and the same program. Most lossy compression schemes can compress a file by varying amounts ranging over a 10:1 or larger range. Some schemes will analyze the file in sgements, estimate the maximum amount of compression for a given level of sound quality, and actually change the amount of compression of that file segment to optimize file size and sound quality. This will be repeated again, different amounts of compression will be chosen for each file segment, and this will be repeated again and again over the duration of the file.

The idea that expensive equipment is required to effectively hear the adverse effects of excess lossy compression fails because problematical situations can be often detected with headphones costing $50 and portable digital players in the same price range. Simply picking a different lossy compression methodology or degree of compresion can correct the situation with the same music and equipment. Good quality speakers costing less than $200 a pair can be useful tools because most lossy compression artifacts affect the upper frequency ranges so mongo bass response is not usually needed for critical listening. Generally, a good quality pair of headphones or earphones can make any adverse effects due to lossy compression more noticeable than a far more expensive pair of speakers.

A key point is that the methodology of lossy compression and the kind of music are critical. For example MP3 files have been around for about 15 years. 10 years ago it was far easier to detect problems when they existed for a given amount of compression.

The correct methodology for detecting problems with lossy compression is a double blind test using music known to be especially demanding. Modest amounts of degradation may only be noticeable with direct comparisons unless specific artifacts can be heard.
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post #8 of 23 Old 06-23-2013, 11:23 AM - Thread Starter
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I've listened to a bluray with high def audio at my dads house and there is no difference between hd audio and optical audio. The picture quality is better in 1080p than 1080i with less screen jutter.
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post #9 of 23 Old 06-23-2013, 11:55 AM
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Quote:
Originally Posted by Kascnef82 View Post

I've listened to a bluray with high def audio at my dads house and there is no difference between hd audio and optical audio. The picture quality is better in 1080p than 1080i with less screen jutter.

A more correct response was you didn't hear a difference. Also in most cases BD's are encoded at 1080p/24 or 1080i/60. In general film judder happens when film based (24fps) content is shown at 60Hz (aka: 3:2 Pulldown).
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post #10 of 23 Old 06-23-2013, 04:01 PM
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In addition to compression, high frequency information is thrown away beyond the highest frequency at the moment of encoding. That is how these codecs can have such great reduction in bit rates. These high frequencyies can never be replaced. If you are listening to background music, or watching a movie, then this is of little consequence. If you are recording to preserve an event, I suggest you use a lossless recording method.
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post #11 of 23 Old 06-23-2013, 06:04 PM
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Nearly all Blu-rays (except a handful of titles) have 48kHz audio tracks, what's 'high def' about it? You wouldn't normally call a DVD-A with 48kHz tracks 'high rez'.

Audiosceptics accept audio trials using 25 people. A recent Oxford study with over 353,000 patient records from 639 separate clinical trials shows for every 1,000 people taking diclofenac or ibuprofen there would be 3 additional heart attacks, 4 more cases of heart failure and 1 death every year.

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post #12 of 23 Old 06-23-2013, 07:23 PM
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Originally Posted by Tazishere View Post

In addition to compression, high frequency information is thrown away beyond the highest frequency at the moment of encoding. That is how these codecs can have such great reduction in bit rates. These high frequencyies can never be replaced. If you are listening to background music, or watching a movie, then this is of little consequence. If you are recording to preserve an event, I suggest you use a lossless recording method.
?? I have never heard that lossless codecs discard any material that is not restored during decompression. With lossless, the output of the decoder is identical to the input of the encoder. If you are talking about how material is initially recorded, i don't see how that is relevant to the issues being discussed in his thread. If you are saying codecs such as TrueHD and dts-MA produce outputs that are different than the inputs, I think you are mistaken.

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Nearly all Blu-rays (except a handful of titles) have 48kHz audio tracks, what's 'high def' about it? You wouldn't normally call a DVD-A with 48kHz tracks 'high rez'.
I don't understand your point here. Nearly all movies are mastered at 48kHz. If you are simply defining movies as lacking high def audio because they don't use 96kHz or higher sampling rates, I suppose that's true. But, why does that matter?
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post #13 of 23 Old 06-23-2013, 07:39 PM
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Originally Posted by Kilian.ca View Post

Nearly all Blu-rays (except a handful of titles) have 48kHz audio tracks, what's 'high def' about it? You wouldn't normally call a DVD-A with 48kHz tracks 'high rez'.

What about 24 bit? To me that's at least equally as important as if it's 96 or 192 khz sampling.
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post #14 of 23 Old 06-23-2013, 08:10 PM
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24 bit is pretty common on Blu-ray
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post #15 of 23 Old 06-25-2013, 02:59 PM
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Originally Posted by Tazishere View Post

In addition to compression, high frequency information is thrown away beyond the highest frequency at the moment of encoding. That is how these codecs can have such great reduction in bit rates. These high frequencyies can never be replaced. If you are listening to background music, or watching a movie, then this is of little consequence. If you are recording to preserve an event, I suggest you use a lossless recording method.

IIRC, at low bitrates, MP3s first take the treble to mono, then begin rolling it off, ultimately rolling off low enough to be quite audible. IDK that much of that goes on at bitrates used on movies. At any rate, I'm quite certain I've seen multiple sources say that the output of lossless compression is bit-for-bit identical to the incoming digital signal. If they are bit for bit identical, they'll sound the same, even if one was stored for a while in a "zipped" file. Even if highs are lost, it's no more mysterious or complex to capture them for the lossless add-on than it is to capture the sounds that are eliminated based on masking effects. The lossy "core" is indeed lossy, but the lossless formats contain the "lost" information in a sort-of "zipped" format, and when you play the lossless rack, they add all that together for the aforementioned bit-for-bit identical signal.
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post #16 of 23 Old 06-25-2013, 03:23 PM
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Originally Posted by Tazishere View Post

In addition to compression, high frequency information is thrown away beyond the highest frequency at the moment of encoding.

Not necessarily.

Depends on the codec and the parameters given to it. You seem to be unware of the fact that compression software can have a goodly list of parameters that change the ground rules for compressing files.

Never happens with lossless codecs.
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post #17 of 23 Old 06-25-2013, 03:25 PM
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Nearly all Blu-rays (except a handful of titles) have 48kHz audio tracks, what's 'high def' about it? You wouldn't normally call a DVD-A with 48kHz tracks 'high rez'.

What about 24 bit? To me that's at least equally as important as if it's 96 or 192 khz sampling.

People who design codecs are often well-trained in psychoacoustics or the science of what actually matters related to sound quality. If you know what matters, you know that even 16 bits is overkill.

The limits of human perception are around 16 KHz bandpass and 13-14 bits.
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post #18 of 23 Old 06-26-2013, 03:50 AM
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...If you know what matters, you know that even 16 bits is overkill....
....but I like my sound to go to 144dB.biggrin.gif
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post #19 of 23 Old 06-26-2013, 05:29 AM
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Originally Posted by William View Post

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Originally Posted by arnyk View Post

...If you know what matters, you know that even 16 bits is overkill....
....but I like my sound to go to 144dB.biggrin.gif

;-)

In reality 144 dB at frequencies in the audio band can kill or at least really hurt you. People work in environments that loud on aircraft carrier decks and the like, but they are dressed for the occasion.
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post #20 of 23 Old 06-26-2013, 04:27 PM - Thread Starter
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What is the loudest bluray you've heard? For me its dark knight rises and a bunch of dts ma discs.
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post #21 of 23 Old 06-27-2013, 09:09 AM
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Quote:
Originally Posted by BIslander View Post

?? I have never heard that lossless codecs discard any material that is not restored during decompression. With lossless, the output of the decoder is identical to the input of the encoder. If you are talking about how material is initially recorded, i don't see how that is relevant to the issues being discussed in his thread. If you are saying codecs such as TrueHD and dts-MA produce outputs that are different than the inputs, I think you are mistaken.
I don't understand your point here. Nearly all movies are mastered at 48kHz. If you are simply defining movies as lacking high def audio because they don't use 96kHz or higher sampling rates, I suppose that's true. But, why does that matter?

I wasn't talking about lossless codecs. I was referring to the way lossy codecs work. I can't site a reference on the internet. I tried to google how lossy codecs work, but I couldn't find what I was looking for. I just know that sometime in the past, I learned that lossy codecs discard high frequencies beyond the highest frequency at the moment. That's how they can be so lossy. Compression alone isn't enough.
Lossless codecs on the other hand, don't discard high frequency information. There may be some ambience information in there. They compress the high frequency information instead.
So, although an MP3 can record 20-20,000 hz, it doesn't always do it if there isn't information above the highest momentary frequency.
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post #22 of 23 Old 06-27-2013, 09:51 AM
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^^ This is about data compression, not dynamic range compression. The encoder removes some of the data and the decoder puts it back. Lossy codecs remove so much data that some of it cannot be restored. The challenge is how to discard data that won't be missed. So, yes, very high frequencies beyond human hearing get thrown out, as are elements that are buried under other sounds. At the higher bitrates, lossy codecs rival lossless in quality.
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post #23 of 23 Old 06-27-2013, 10:01 AM
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Quote:
Originally Posted by Tazishere View Post

...Lossless codecs on the other hand, don't discard high frequency information. There may be some ambience information in there. They compress the high frequency information instead....
Lossless codecs (TrueHD, DTS-HD, FLAC, ALAC,... compress all the digital data. It is then decompressed to it's 100% original state. I think you are confusing dynamic range compression with digital data compression. There is NO dynamic range compression in lossless (or even lossy unless you go to a lower bit depth and/or extremely low bit rate). Lossless after decoding is 100% bit for bit identical to it's source (100100110001000 will be 100100110001000 after decoding)
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