Missing Format - Blu-Ray Audio

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I’d like to suggest the addition of a Blu-Ray Audio format, similar to how DVD-A exists as a sub-format to DVD. I have added a few (classical) albums that are Blu-Ray audio (this sub-collection for Karajan Complete: https://musicbrainz.org/release/8e70aa7d-c0b6-4fc8-a9b4-9f6f7a7a0ee2 and discs 94-99 in the Pavarotti Opera set: https://musicbrainz.org/release/4a02351e-2759-4e97-99c0-94eb3d89a115). I have used the Blu-Ray format, but this implies video to many people, so having a separate format would be helpful to delineate the two.

Barring that, is there a more appropriate format instead of “Blu-Ray”?

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I would not be in favor of this. DVD-Audio is a technically different format, with MLP encoded audio in the AUDIO_TS folder.

There is no technical difference between how an “audio only” Blu-ray disc is authored. It is the same format, the only difference is the lack of significant video content which would be evident from the track listing (no videos).

Has any particular problem arisen from people thinking these releases are video?

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High Fidelity Pure Audio (the Blu-ray format in question) has specific connotations: It only uses lossless encoding formats, and audio is always encoded at 24 bits per sample, with a minimum sampling rate of 96 KHz.

Some Blu-ray discs encode audio as DTS-HD High Resolution Audio, which is a lossy format. HFPA discs do not use this format. They only use DTS-HD Master Audio (the lossless DTS-HD implementation), Dolby TrueHD, or LPCM. Any of these lossless formats may be implemented with Blu-ray video, but HFPA uses them exclusively. The English Wikipedia article on HFPA is awkwardly worded, and gives the impression that lossless encoding is optional for HFPA, too. That is incorrect.

As for bitrate and sampling rate: A Blu-ray disc might also use 16-bit or 20-bit encoding, or sampling rates as low as 48 KHz, but HFPA uses 24/96 at a minimum.

So, if a BD package has the HFPA logo on it, all of the above is what that means. I’d say it’s worthwhile to submit a ticket to add it to the list.

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Thanks for the responses. In the case of the albums I linked, they are definitely HFPA since it’s emblazoned on the disc envelopes.

No major issues have arisen, although one editor questioned its use because it was assumed Blu-Ray = video. For me, it’s more a question of clarity and accuracy instead of overloading the semantics to suit.

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But that still does not make HFPA a separate format. It’s a convention on what features of a format to use. A bit like the high-bitrate Criterion Collection dvds.

I agree, also, HFPA isn’t the only convention used for releasing music on Blu-ray. Others include “Pure Audio” and Naxos’s “High-Definition Audio Disc”.

All that’s needed for an audio format is a specification. The features and requirements of that specification may be a subset or a superset of another specification. In this case, compatibility with existing hardware was a requirement for the spec. (Remember that DVD-Audio had some compatibility issues.) But you’re right: just using features doesn’t make a separate format.

I think a more accurate comparison is between CD-ROM and CD-ROM XA (in the Yellow Book standard), or CD and CD+ (in the Red and Blue Book standards). CD-ROM XA and CD+ are both multisession formats, but they organise the sessions in a predictable way, and store specific types of data there in predefined locations. When you don’t have a specification that accounts for special use cases, you get problems with usability or compatibility. Some early game CD-ROMs had CD audio in the same session as the data track. It was possible to play those tracks in a CD player, but the Yellow Book specification made no allowances for this. Since the data track was in the same session, it showed up in the playlist. Playing the data track made a loud, irritating screeching sound that could go on for ages if allowed to.

Problems like that had already been solved by the time Blu-ray was invented. But there was still an unsolved problem left over from the DVD era: How do you make Blu-ray (which was designed for video) usable on a headless sound system? HFPA and Pure Audio took different approaches to this.

HFPA just programmes the menus such that one doesn’t need a screen to choose a stream (7.1, LPCM, etc.). Pure Audio went a step further and colour-coded each audio stream to the red, yellow, green, and blue buttons on the Blu-ray remote. That colour coding is now part of AES-21id-2011, which is the Pure Audio spec. The Blu-ray standard allows content makers to programme the coloured buttons differently on every disc, but Pure Audio makes their behaviour consistent. So, what you have is a minimum standard for how sound is encoded, and how it is accessed.

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