Newbie question..Codecs, lossless & other sound questions?

You're familiar with Dolby Digital and DTS, are you not? Those digital surround formats were introduced over a decade ago. Since then, technology has progressed.

The HD-DVD and Blu-ray formats provide more bandwidth and capacity for audio. The next-generation codecs from Dolby (TrueHD) and DTS (DTS-HD MA) take advantage of that extra bandwidth and capacity to provide higher-fidelity audio. These new formats can provide audio quality bit-for-bit identical to the original studio master, rather than the MP3-like quality we had with DVD. In order to experience this new audio, you need new decoders. The decade-old Dolby Digital and DTS decoders found in existing receivers do not support these new audio formats.

Blu-ray and HD-DVD releases always include legacy Dolby Digital or DTS tracks for backward compatibility with older equipment. However, if you want to experience the new and improved, higher-quality Dolby TrueHD or DTS-HD surround sound on these disks, you need a decoder that supports those formats. Some Blu-ray and HD-DVD players include these decoders, or have announced an upcoming software update to add that capability to the existing hardware, but many do not.

Almost all BDs have either DD or DTS, but not all.

The Blu-ray specification requires that any title with a TrueHD or DTS-HD track include a legacy Dolby Digital or DTS 5.1 surround signal for backward compatibility with older systems and players.

I expect you're referring to one of the few titles with uncompressed audio (LPCM) which lacks a DD5.1 or DTS track. Even on these titles, which you can count on one hand, provide stereo sound for those using optical connections and 5.1 surround to those using 5.1 analog connections.

Yes. I didn't understand that you meant all BDs with those audios will have the legacy, i thought you were saying in general.

I've only heard the PCM sound on a couple of BDs and compared it to the DD (not the new Dolby true stuff) and it was SO much better. I could tell instantly.

I'm confused about the new HD DD and HD DTS codecs. In the past, DD and DTS existed to overcome limits in the amount of storage data available to reproduce 5.1 discrete channels.

With BD, there is sufficient capacity for 5.1 LPCM or even higher, which is CD quality audio for 5.1 channels. My question is why is this worse than HD DVD and HD DTS? My Sony BDP-S1 can output LPCM to my older receiver which actually has 8 channel analog inputs (I wish I could use all of them).

Is it that LPCM is 48/16 and these new codecs are 96/24? From my understanding, 48/16 is very good and most of the issues with it were due to early mastering technology.

Can anyone comment about whether HD DD and HD DTS sound better than LPCM? Obviously, these HD DD and HD DTS codecs are compressing the signal even if they claim it is lossless compression. Thanks.

All modern films are mastered with 24/48 audio. Employees at these mastering facilities, as well as the individuals doing the theatrical mixes, have said as much on this forum. Even paidgeek has said as much over on the Industry Insiders forum.

Due to the high bandwidth and space requirements of uncompressed audio, most studios downconvert 24/48 master audio to lower 16/48 fidelity for use on Blu-ray disk. Only a handful of current Blu-ray disks with LPCM feature master quality audio; more than 90% of all releases with LPCM feature inferior 16-bit audio. Paidgeek -- the representative from Sony Home Video -- has said several times over in the HDTV Software Media forum that Sony intends to stick with 24-bit -> 16-bit downconversion on LPCM releases for the forseeable future, due to bandwidth constraints.

Rather than downgrade the 24/48 master audio to lower 16/48 fidelity, some studios (FOX) have chosen to losslessly pack or "zip" these audio masters with DTS-HD MA or Dolby TrueHD. Once unpacked or "unzipped" by a player or future HDMI 1.3 receiver, the resulting output is a 24/48 LPCM track that is bit-for-bit identical to the original studio master.

LPCM
2 hours @ 5.1 16/48 LPCM = 4.14 Gbytes @ 4.6 Mbps (used today by most Blu-ray disks with LPCM)
2 hours @ 7.1 16/48 LPCM = 5.52 Gbytes @ 6.13 Mbps
2 hours @ 5.1 24/48 LPCM = 6.21 Gbytes @ 6.9 Mbps
3 hours @ 5.1 24/48 LPCM = 9.32 Gbytes @ 6.9 Mbps
2 hours @ 7.1 24/48 LPCM = 8.28 Gbytes @ 9.2 Mbps
3 hours @ 7.1 24/48 LPCM = 12.42 Gbytes @ 9.2 Mbps
2 hours @ 7.1 24/96 LPCM = 16.56 Gbytes @ 18.4 Mbps
3 hours @ 7.1 24/96 LPCM = 24.84 Gbytes @ 18.4 Mbps

Dolby TrueHD (comparable to DTS-HD MA)
2 hours @ 5.1 16/48 TrueHD = 1.26 Gbytes @ 1.4 Mbps ABR
2 hours @ 5.1 24/48 TrueHD = 3.06 Gbytes @ 3.4 Mbps ABR
3 hours @ 5.1 24/48 TrueHD = 4.59 Gbytes @ 3.4 Mbps ABR
2 hours @ 7.1 24/48 TrueHD = 4.23 Gbytes @ 4.7 Mbps ABR
3 hours @ 7.1 24/48 TrueHD = 6.35 Gbytes @ 4.7 Mbps ABR

Both TrueHD and DTS-HD MA use variable bit rates, so the bit rate varies by the "complexity" of the soundtrack during the film. The ABR notation above refers to average bit rate.

If studios were to use BD50 exclusively for just the feature in AVC, audio in LPCM, and a few extras, this wouldn't be an issue. However, 80% of announced, upcoming Blu-ray titles use BD25, and more than two-thirds of the remainder slated for BD50 use MPEG-2. Moreover, studios are expected to add more and more extras to their disks. Later this year, we're expected to see the first Blu-ray releases with BD-Java and true PIP commentary, which will subtract additional bits from the available mux rate.

With BD25, you can forget 24/48 LPCM on all but the shortest movies. Even with BD50, LPCM at master quality 24/48 starts to eat into the picture quality when MPEG-2 is used. Subtract 7.1 24/48 from the available mux rate and you're left with with a bit over 45Mbps. Subtract the three foreign language tracks in 640Kbps Dolby Digital and you are left with 43Mbps and change. Subtract the picture-in-picture video commentary featured on upcoming BD-Java disks and you are left with 36-38Mbps. Subtract overhead and interactivity and you're left with 34-36Mbps. If all studios were to abandon MPEG-2 in favor of AVC, that would be fine for all but the longest movies, but that's not going to happen.

When less than 10% of announced Blu-ray titles feature the combination of BD50 and AVC, we need the advanced audio codecs to get master quality, 24-bit / 48kHz audio.


Dolby TrueHD and DTS-HD MA are just lossless packing methods for LPCM. Said a different way, they are basically zip files containing LPCM. This lossless packing may be unnecessary on most BD50 disks with AVC video, but again, only a small minority of announced titles actually use both BD50 and AVC.

Examples of Blu-ray releases with 24/48 LPCM tracks include Chicago, Pearl Harbor, The Prestige, and The Wild. Except for The Wild, all of these are BD50 releases, and three of them use AVC.

Even if all studios were to use the combination of BD50 and AVC, that might still prove inadequate for high-fidelity 24/48 LPCM audio on the longest films, particularly as studios add interactive disk features. Consider the film Dances with Wolves. This has a run time of 226 minutes, which means that the average bit rate available for that title on BD50, assuming no extras is approximately 29 Mbps.

Subtract 7.1 24/48 LPCM from that and you're left with with a bit under 20Mbps. Subtract the three foreign language tracks in 640Kbps Dolby Digital and you are left with 18Mbps and change. Throw in a picture-in-picture video commentary featured on upcoming BD-Java disks and you're left with 10-12Mbps ABR for video.

Does that sound good to you?

Other recent films of similar length include King Kong, The Green Mile, The Lord of the Rings: Return of the King, Spartacus, and Titanic, as well as classics such as Apocalypse Now, Ben Hur, Lawrence of Arabia, and Schindler's List.

OK, so when will we see a player capable of playing the loss-less codecs over optical or analog cables? I have a Yamaha Z9 receiver and am not inclined to spend another $3500 for an HDMI receiver.

The Sigma Designs SoC processor used in the existing Panasonic, Pioneer, and Sony Blu-ray players will decode Dolby Digital Plus, Dolby TrueHD (lossless), and DTS-HD High Resolution, but not DTS-HD Master Audio (lossless). However, to get that functionality, the manufacturer must support those features in firmware. Panasonic has announced the intention to add decoding for those codecs with a software update, whereas Pioneer and Sony have not. Sony and Pioneer may want customers to buy new players to get that capability.

Sigma Designs just released a revised version of their chip with more processing power which adds support for DTS-HD Master Audio. Many of the second-generation players coming in June, July, and August should use that chip.