What is lossless audio?

[Atreyu]

There may have been an earlier thread devoted to this but I'm not sure.
What is Lossless/HD Master Audio? What are the differences and what makes it better than say Dolby 5.1?

[Big Daddy]

Read https://forum.blu-ray.com/audio-theo...io-codecs.html .

[42041]

a CD is lossless (well, uncompressed)
an MP3 is lossy
perceptual codecs throw out audio information you ear is unlikely to hear, but it's not a perfect copy.

[Big Daddy]

Originally Posted by 42041

a CD is lossless (well, uncompressed)
an MP3 is lossy
perceptual codecs throw out audio information you ear is unlikely to hear, but it's not a perfect copy.

Be careful about using the word "uncompressed". Compression is not the same thing as lossy and lossless. We can have lossy compression and lossless compression. Dolby Digital and DTS surround are examples of lossy compression and Dolby TrueHD and DTS-HD MA are examples of lossless compression. PCM (or LPCM) is lossless and uncompressed.

[Atreyu]

Thanks this info sure clears up alot for me I really appreciate it.

[Damage Inc.]

I think you could also roughly compare homevideo-audio to separate music-audio.
As in, DVD-quality would be like MP3-quality and BD-quality would be like CD-quality.
Except you of course have the different codecs, but quality-wise it's pretty similar.

[Hammie]

Originally Posted by Damage Inc.

I think you could also roughly compare homevideo-audio to separate music-audio.
As in, DVD-quality would be like MP3-quality and BD-quality would be like CD-quality.
Except you of course have the different codecs, but quality-wise it's pretty similar.

Actually, I would say DVD and CD are similar and BD and SACD or BD-A are similar.

And then there is DVD-A. Does that go with DVD or BD?

I'm not even sure if that is 100% accurate.

[Damage Inc.]

Originally Posted by Hammie

Actually, I would say DVD and CD are similar and BD and SACD or BD-A are similar.

And then there is DVD-A. Does that go with DVD or BD?

I'm not even sure if that is 100% accurate.

Hm, I think you're confusing that because DVD-Audio is considered better quality than CD.
Obviously because there is more space, there's better audio for the music.
But the audio for film on DVD isn't nearly as good I believe, unless it's DTS maybe...
Cause I've seen bitrates of steady 192kb/s, which is just like MP3 only a different amount of channels.
That's why I figured, DVD-audio for films might be equivalent to MP3-quality?

Hm, I agree that CD-audio is probably not nearly as good as BD-audio for films.
But I meant as in, stepping up from DVD-audio to BD-audio,
is probably much like going from MP3-quality to CD-quality.
While only roughly being similar quality in a way, not exactly technically and all that.

[Jwilly019]

Originally Posted by Hammie

Actually, I would say DVD and CD are similar and BD and SACD or BD-A are similar.

And then there is DVD-A. Does that go with DVD or BD?

I'm not even sure if that is 100% accurate.

DVD-A is similar to SA-CD and BD.

Justin

[Big Daddy]

DVD-A uses LPCM or Meridian Lossless Packing (MLP) up to 6 channels of lossless audio. MLP is licensed by Dolby. Dolby TrueHD is based on MLP and offers up to 8 channels of lossless audio.

SACD uses a different codec called DSD.

[Hammie]

I think there are too many differences that would not allow it to be compared accurately. Much like the Apple and Oranges comparison. The only commonality is that they are fruit.

[BIslander]

PCM is the basic digital audio format used with CDs, DVDs, and Blu-rays. Movie masters are usually recorded as PCM. The quality of a PCM master depends on the sample rate and bit depth used to make the recording.

DD 5.1 and DTS are lossy compression codecs that were developed to save the space needed to squeeze a 5.1 movie soundtrack on a film or a CD. The PCM originals are too big to fit on films, CDs, and the audio area of DVDs. So, Dolby and DTS each developed its own codec that compresses (zips) the PCM file down to a size that will fit where it needs to go. The files have to be squeezed so much that some of the data removed during compression cannot be restored during decompression. That's why they are called lossy codecs - some of the data is lost.

TrueHD and dts-MA are lossless compression codecs. Blu-ray discs have more space. So, the PCM files don't need to be compressed as much to fit on a disc. (Actually, they don't have to be compressed at all. BDs can handle multichannel PCM tracks. But, studios still want to conserve space which can be used for more extras.) When a lossless file is decompressed, everything that was removed during compression is put back in - nothing is lost.

DVD-Audio discs are DVDs formatted with lots of space for audio instead of video. The DVD-Audio format uses MLP, which is another lossless compression codec. As Big Daddy noted, Dolby uses MLP as the foundation for TrueHD.

So, you have the original, uncompressed PCM. TrueHD, dts-MA, and MLP are all ways of losslessly compressing the original PCM to save space. When decompressed, each of those codecs produces an output identical to the PCM original. CDs are also encoded using PCM. But, because of size restrictions, CDs are limited to two channels of PCM with 44.1kHz sampling rates and 16 bits. By comparison, a DVD-Audio disc can have up to six channels at 96/24 or stereo at 192/24.

SACD is not based on PCM. It uses DSD - a completely different type of digital audio. But, it's a format that can support multiple channels of high resolution audio. So, in terms of quality, it is generally equated with uncompressed PCM.

[danfaz]

Bislander...perfect post!

[Dubstar]

Originally Posted by BIslander

PCM is the basic digital audio format used with CDs, DVDs, and Blu-rays. Movie masters are usually recorded as PCM. The quality of a PCM master depends on the sample rate and bit depth used to make the recording.

DD 5.1 and DTS are lossy compression codecs that were developed to save the space needed to squeeze a 5.1 movie soundtrack on a film or a CD. The PCM originals are too big to fit on films, CDs, and the audio area of DVDs. So, Dolby and DTS each developed its own codec that compresses (zips) the PCM file down to a size that will fit where it needs to go. The files have to be squeezed so much that some of the data removed during compression cannot be restored during decompression. That's why they are called lossy codecs - some of the data is lost.

TrueHD and dts-MA are lossless compression codecs. Blu-ray discs have more space. So, the PCM files don't need to be compressed as much to fit on a disc. (Actually, they don't have to be compressed at all. BDs can handle multichannel PCM tracks. But, studios still want to conserve space which can be used for more extras.) When a lossless file is decompressed, everything that was removed during compression is put back in - nothing is lost.

DVD-Audio discs are DVDs formatted with lots of space for audio instead of video. The DVD-Audio format uses MLP, which is another lossless compression codec. As Big Daddy noted, Dolby uses MLP as the foundation for TrueHD.

So, you have the original, uncompressed PCM. TrueHD, dts-MA, and MLP are all ways of losslessly compressing the original PCM to save space. When decompressed, each of those codecs produces an output identical to the PCM original. CDs are also encoded using PCM. But, because of size restrictions, CDs are limited to two channels of PCM with 44.1kHz sampling rates and 16 bits. By comparison, a DVD-Audio disc can have up to six channels at 96/24 or stereo at 192/24.

SACD is not based on PCM. It uses DSD - a completely different type of digital audio. But, it's a format that can support multiple channels of high resolution audio. So, in terms of quality, it is generally equated with uncompressed PCM.

though I never understood why lossy sound occured on DTS laserdiscs, where it seems like there would be more than enough space to encode both video and audio.

[Damage Inc.]

Originally Posted by Dubstar

though I never understood why lossy sound occured on DTS laserdiscs, where it seems like there would be more than enough space to encode both video and audio.

Wouldn't that be the same lossy audio as on DVD?
Cause DTS just means it's that encoder, but not that it's lossless.
Perhaps higher bitrates, which was the case with DVD-DTS,
but I don't think there would be space for lossless audio in addition to the video on LaserDisc.

Hm, I just read that apparently the bitrates for DTS on LaserDiscs were higher than those on DVDs.
But seeing the numbers I also have seen DVDs with similar quality DTS though.
Still, they put compressed, thus lossy, DTS-tracks on LaserDisc.
I believe still due to capacity-limitations.

[WiWavelength]

The LaserDisc format dates to the late 1970s. LDs were not huge, digitally encoded aluminum discs. Rather, they were huge, analog FM encoded aluminum discs. Somewhat akin to laser read LPs, LDs contained analog video & analog audio. Digital audio was actually a later addition, and it was limited to two channel 16 bit 44.1 kHz PCM -- the same as CD Red Book audio.

2 * 16 * 44100 = 1411200 bps

Lossy DTS on LD compressed 5.1 channels w/in the PCM data rate calculated above. Additionally, as I understand it, DTS on LD was based upon the consumer 44.1 kHz sampling rate. However, most film digital audio production is based on the professional 48 kHz sampling rate. So, as part of encoding to lossy DTS on LD, most film soundtracks had to undergo sample rate conversion from 48 kHz to 44.1 kHz.

Lossy DTS on DVD also compressed 5.1 channels w/in two PCM data rates calculated below.

2 * 16 * 48000 = 1536000 bps

1 * 16 * 48000 = 768000bps

The first is full rate lossy DTS on DVD; the second is half rate lossy DTS on DVD. Both are based upon the professional 48 kHz sampling rate. As such, most film soundtracks did not need to undergo sample rate conversion.

AJ

[BIslander]

Originally Posted by Dubstar

though I never understood why lossy sound occured on DTS laserdiscs, where it seems like there would be more than enough space to encode both video and audio.

Laserdisc predates TrueHD and dts-MA and HDMI. So, you'd be talking about PCM, if the discs had enough space, and multichannel analog outputs.