Topic: Naming: Bitstreaming vs Passthrough (Read 8889 times)

Matt · « **on:** April 09, 2013, 11:48:37 am »

When MC plays a stream of audio data that it's not decoding and can not apply DSP to, we currently call this "bitstreaming". This means we're just passing the bits from the input to the output. We don't necessarily understand the bits and have no ability to change them.

This was common years ago with AC3 over S/PDIF. Today it's sometimes used to send the audio from a video over HDMI for decoding by a receiver (although we recommend decoding on the computer). It's also common with DSD devices.

Is this mode best called "bitstreaming" or "passthrough"?

We have always used the term "bitstream", but somebody here is arguing that "passthrough" is more understandable and descriptive.

Thoughts?

MrC · « **Reply #1 on:** April 09, 2013, 11:55:47 am »

I voted passthrough. Bitstreaming to me simply indicates a stream of 0's and 1's, and has no relation to how those were produced.

6233638 · « **Reply #2 on:** April 09, 2013, 01:03:14 pm »

I have always seen this referred to as bitstreaming on receivers and playback devices. For example, the Playstation 3 gives you the option to output "Bitstream" or "Linear PCM"

jmschnur · « **Reply #3 on:** April 09, 2013, 04:22:47 pm »

Passthrough gives a better sense of what is going I think.

Neco · « **Reply #4 on:** April 10, 2013, 01:15:49 am »

Compromise.

Bitstreaming (Passthrough) or Passthrough (Bitstreaming)

jmone · « **Reply #5 on:** April 10, 2013, 01:24:31 am »

What! No Pure Direct option! It is bitstreaming for me.

InflatableMouse · « **Reply #6 on:** April 10, 2013, 03:47:40 am »

I think you're getting caught up in symantics

.

Technically, bitstream makes less sense because unless you're outputting analog, its all a "stream of bits".

The term 'bitstream' in this context means the uncompressed, unaltered track as it appears on the source. If someone says he wants to bitstream DTS-HD MA, we know exactly what he wants to accomplish and we don't think about that stream being decoded by MC and presented as a LPCM 'bitstream'.

Therefore, I voted bitstream simply to avoid confusion. But as suggested above, including 'passthrough' between brackets is a good thing too.

jmone · « **Reply #7 on:** April 10, 2013, 04:10:11 am »

I've changed my mind after looking at how the current option is layer out in MC and would suggest a change.

Currently there is a Diag for "DSP and Output Format" and One for "Bitstreaming". Instead of "Bitsreaming" how about "Enable DSP Processing / Decoding" and then have the options as "All (Default)" or "Custom" that then allow users to say which ones are bitstreamed over HDMI or SPDIF .

That way you have no Bitstream Vs Decoded as it is not really accurate when you then discuss what you do with say LPCM tracks as there is no decoding either way but just a DSP toggle.

fitbrit · « **Reply #8 on:** April 10, 2013, 09:05:26 am »

Quote from: Neco on April 10, 2013, 01:15:49 am

Compromise.

Bitstreaming (Passthrough) or Passthrough (Bitstreaming)

This is what I would vote for too.

csimon · « **Reply #9 on:** April 10, 2013, 09:29:49 am »

I vote Bitstream. Passthrough is indeed more descriptive, but Bitstream's meaning is universally adopted and understood - it's in my Freesat set-top-box for example. It's a term that means passing through the audio without decoding. Passthrough may be more descriptive however it's not universally used for that concept in that context. I would have to think twice if someone talked to me about audio passthrough in this context. Passthrough, to me, means for example an HDMI signal being available on an AV Amp's output socket as well as being ingested and processed by the amp. It also means an RF signal being daisy-chained between several devices on its way from aerial to TV, it will hopefully not get degrdaded on the way but it may do. I think, in the context we are using it, Bitstreaming means an encoded digital audio signal being sent to a playing device which will decode the signal itself, rather than having the signal decoded before it's sent.

Essentially, the accepted meaning of Passthrough I think is duplicating the input to be sent to two different paths - one of which is consumed by some processing and the other goes onto a daisy-chained device which should be unaware that it is receiving a copy, although the copy may not be completely identical to the original. Bitstreaming means un-decoded or un-converted, i.e. not decoding or converting a single path.

mojave · « **Reply #10 on:** April 10, 2013, 10:18:10 am »

I voted for bitstreaming since that is the term generally used in HTPC forums and by hardware.

I think of passthrough as a term that includes both audio and video, while bitstreaming refers just to the audio. With passthrough, the video and audio are untouched. A receiver using passthrough (sometimes called standby pass) will send both video and audio on the TV without any video resizing or audio decoding. Bitstreaming is used for the audio when the video and audio have been separated with processing done to the video, but not the audio.

Quote

BTW, How does ASIO fit in here? I would of thought it is a form of "bitstreaming",in this case passing non converted LPCM to an external DAC for the analogue conversion. I notice that the bitstreaming option remains present whether ASIO is selected or not.
TIA

ASIO is used when the audio is decoded to PCM. Bitstreaming is used when the audio is still encoded as Dolby Digital, DTS, etc. Since you might play music and movies through the same zone, you could use ASIO for some sources and bitstreaming for other sources which is why the bitstreaming option is still available.

MrC · « **Reply #11 on:** April 10, 2013, 11:50:57 am »

Quote from: csimon on April 10, 2013, 09:29:49 am

...but Bitstream's meaning is universally adopted and understood...

The problem is... it is not universally understood, when the realm of audio converges with the realm of computer science (where it has an altogether different meaning).

https://en.wikipedia.org/wiki/Bitstream

6233638 · « **Reply #12 on:** April 10, 2013, 11:53:29 am »

Quote from: MrC on April 10, 2013, 11:50:57 am

The problem is... it is not universally understood, when the realm of audio converges with the realm of computer science (where it has an altogether different meaning).

https://en.wikipedia.org/wiki/Bitstream

Quote from: https://en.wikipedia.org/wiki/Bitstream

See also
Bitstream Format

I have never encountered any devices that use "Passthrough" as the description for this feature - it has always been referred to as "Bitstream"

Hendrik · « **Reply #13 on:** April 10, 2013, 12:05:22 pm »

I never understood where "Passthrough" comes from, because it just doesn't fit properly, in my mind.
What do you pass it through? The cable? The software decoder maybe, but thats reaching, imho, especially because the decoder (at least in a PC) is actually the one that takes the audio bitstream and brings it into a format suited for SPDIF/HDMI transport.

When a AVR talks about passthrough, its literal "pass through the AVR untouched", meaning the audio and/or video is forwarded to the TV without modification, it literally passes through the AVR.

I just don't think its the right word.

MrC · « **Reply #14 on:** April 10, 2013, 12:15:14 pm »

Can't one also make the case that Bitstream equally doesn't make sense along the same lines, as all this data is packet-ized sequences of bytes, delivered in chunks by the software (and perhaps delivered actually by the OS as a bitstream to the device)?

Anyway, its clear the meaning of both terms are vague, and the selections made are based on preference as opposed to actual merit.

Hendrik · « **Reply #15 on:** April 10, 2013, 12:20:40 pm »

"bitstream" or "bitstream format" is commonly used to describe the encoded form of a codec, granted that may not be something everyone knows, but if you do, imho it makes perfect sense.

fitbrit · « **Reply #16 on:** April 10, 2013, 12:21:32 pm »

Quote from: nevcairiel on April 10, 2013, 12:05:22 pm

When a AVR talks about passthrough, its literal "pass through the AVR untouched", meaning the audio and/or video is forwarded to the TV without modification, it literally passes through the AVR.

And similarly, when JRiver does 'passthrough', it literally 'passes through MC untouched', meaning the audio is forwarded to the next component (e.g. AVR) without modification; it literally passes through MC.

Hendrik · « **Reply #17 on:** April 10, 2013, 12:23:52 pm »

Quote from: fitbrit on April 10, 2013, 12:21:32 pm

And similarly, when JRiver does 'passthrough', it literally 'passes through MC untouched', meaning the audio is forwarded to the next component (e.g. AVR) without modification; it literally passes through MC.

But its not untouched, you need to reformat it for HDMI transmission.

InflatableMouse · « **Reply #18 on:** April 10, 2013, 12:32:13 pm »

Quote from: MrC on April 10, 2013, 11:50:57 am

The problem is... it is not universally understood, when the realm of audio converges with the realm of computer science (where it has an altogether different meaning).

https://en.wikipedia.org/wiki/Bitstream

Maybe not universally but within the context that it is being used, at least some devices (most bluray players? at least the ones I've seen and owned) and some other applications use it with the same meaning as MC does currently. Changing it will only lead to more confusion.

Read https://en.wikipedia.org/wiki/HDMI for instance. The term 'bitstream' is used several times throughout the article to indicate an audio stream is left untouched, uncompressed and passed on directly. So I think within the context we speak, the term is understood to mean what MC is using it for.

'Source Direct' is used on some audio equipment to indicate something similar but like passthrough its not quite the same either.

InflatableMouse · « **Reply #19 on:** April 10, 2013, 12:35:52 pm »

Quote from: nevcairiel on April 10, 2013, 12:23:52 pm

But its not untouched, you need to reformat it for HDMI transmission.

Correct me if I'm wrong, but when we say 'untouched' we mean the bits that make up the actual audio, not packet headers, communication handshakes, error correction data and that kind of stuff. So yes, it may need to be repackaged/reformatted but the actual audio data bits stay untouched.

Right?

fitbrit · « **Reply #20 on:** April 10, 2013, 12:46:32 pm »

We should call it the "Not my problem" format.

6233638 · « **Reply #21 on:** April 10, 2013, 12:52:50 pm »

Quote from: fitbrit on April 10, 2013, 12:21:32 pm

And similarly, when JRiver does 'passthrough', it literally 'passes through MC untouched', meaning the audio is forwarded to the next component (e.g. AVR) without modification; it literally passes through MC.

It's not "passing through" MC though - it's originating from it.

JimH · « **Reply #22 on:** April 10, 2013, 12:54:31 pm »

objective/subjective

Vincent Kars · « **Reply #23 on:** April 10, 2013, 02:56:33 pm »

I always wondered what Bitstreaming means.
I’m inclined to call it Output Format but this is already used by DSP Studio for resampling.

Protocol (output)
Because this is what this option controls
None= LPCM?

dean70 · « **Reply #24 on:** April 10, 2013, 04:47:59 pm »

Bitperfect?

Boltron · « **Reply #25 on:** April 10, 2013, 08:09:20 pm »

Bitstream is the common term for this in my experience.

mojave · « **Reply #26 on:** April 10, 2013, 09:52:57 pm »

I used a Toshiba Blu-ray player tonight at church. I checked the settings and one of the audio options was bitstream. I think the others were PCM, re-encode, and analog.

MrC · « **Reply #27 on:** April 11, 2013, 01:04:41 am »

eddyshere · « **Reply #28 on:** April 11, 2013, 05:46:32 am »

+1 for "bitstreaming"

fitbrit · « **Reply #29 on:** April 11, 2013, 09:38:49 am »

Quote from: eddyshere on April 11, 2013, 05:46:32 am

+1 for "bitstreaming"

Despite my comments above, I would have to agree. On other forums, everyone refers to it as bitstreaming, no matter which hardware or software they use. Best to keep the terminology consistent for new users.

glynor · « **Reply #30 on:** April 11, 2013, 12:02:02 pm »

Quote from: Neco on April 10, 2013, 01:15:49 am

Compromise.

Bitstreaming (Passthrough) or Passthrough (Bitstreaming)

I voted Bitstreaming (because that's how it is commonly referred-to in GPU reviews and whatnot).

But +1

jmschnur · « **Reply #31 on:** April 11, 2013, 01:49:22 pm »

If bitstream, add a glossary definition explains that files are sent as saved in computer to device with no encoding ; i.e bit by bit.

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Author Topic: Naming: Bitstreaming vs Passthrough (Read 8889 times)