mp3 bitstream trough SPDIF

[snw]

Hi!
I'm wondering if theres any way to output raw mp3 bitstream trough the spdif port?!
I have a built in mp3 decoder in my harman/kardon cinema amplifier and have never used it
So it would be fun to test if it works =) And by the way... Is it possible to burn a mp3 cd
and play it back on a normal cd player and have a mp3 compilant bitstream trough the digital out on the cd player?
I've heard this works with dts and ac3...
I'll be happy for any answers :)

[MaTTeR]

I play MP3, Vorbis, AAC and every other format over SPDIF perfectly. Due to the specs though, you will only hear 2ch playback of course.

Is it possible to burn a mp3 cd
and play it back on a normal cd player and have a mp3 compilant bitstream trough the digital out on the cd player? Good question, I've never tried and I suppose it would depend on your stand alone player.

I've burnt DTS WAV files as an Audio CD and they played perfectly on my Sony DVD/CD stand alone.

[snw]

Thanx for the reply!

Originally posted by MaTTeR
I play MP3, Vorbis, AAC and every other format over SPDIF perfectly. Due to the specs though, you will only hear 2ch playback of course.

I suppose that you don't have a vorbis compatible decoder in your amplifier?!
So what you do is to play a PCM stream trough SPDIF... (Except ac3, dts...)

What I was looking for is a way to output the mp3 stream directly to the amplifier without first converting it to PCM in the computer. ;)

[MaTTeR]

Originally posted by snw
[B]I suppose that you don't have a vorbis compatible decoder in your amplifier?! Nobody has one because they don't exist yet ;-)


So what you do is to play a PCM stream trough SPDIF... (Except ac3, dts...) I play everything via SPDIF except multi-channel Vorbis. The MP3 files over SPDIF are automatically seen as PCM to your amp. No conversion is required on your part. Play them natively.

[Antimon]

What he is saying matter is he wants his amp to decode the mp3 not the pc....Why i have no idea.....

But in any event the answer is no.


The computer only passes pcm data to the decoder except for the dts/dolby digital files, which are still delivered as a pcm bitstream i believe, as some sort of square wave which is detected and properly decoded by the amp.

[snw]

Thanks for your replies!

Originally posted by Antimon
What he is saying matter is he wants his amp to decode the mp3 not the pc....Why i have no idea....

Thats right ;) In testing purpose I'd like to compare the quality of the decoder in my PC and the one inside the amp.

Originally posted by Antimon
The computer only passes pcm data to the decoder except for the dts/dolby digital files, which are still delivered as a pcm bitstream i believe, as some sort of square wave which is detected and properly decoded by the amp.

I see no reason why this would not be possible with mp3?! In the same way as ac3/dts is delivered and detected by the amp it should be possible to detect mp3... The thing is just to make a filter passing it out trough the spdif as a mp3 bitstream instead of a regular pcm sream...

And in the same way as it is possible to record CDRs with ac3/dts waw and output it trough the digital out on a regular cdplayer I believe it is possible with mp3 if your amp has a mp3 decoder. It's just the tools that's missing...

[Antimon]

I've never seen an amp with a mp3 decoder unless it was incldued with a cd drive, in which case it's reading the data off the cd directly and has no input for it.

But if just an amp with no drive has mp3 suport they must anticipate some way of passing an mp3 bitstream to it.

Well thsi is a long shot...but what if you tried hookingn the mp3 up to the intervideo decoder in graph edit?

Dunno if itwould allow you or if it'd work...but you could try.

[Tes]

Originally posted by snw
I'd like to compare the quality of the decoder in my PC and the one inside the amp.
You have an MP3 decoder in your amp!? What brand and model amp/receiver is it? Does it decode multichannel MP3? What about AAC?

BTW you are probably using a software decoder to play MP3s on your PC (unless you have a hardware MP3 decoder board). So the amp *should* sound better.

[Antimon]

Not nessicarily...after all it's software inteh amp also.....

Enstead of beign on a ahrd drive....it's in a firmware, whats the differnce?

And with digital streams, noise addition cus of hardware componants isn't as much of an issue

If you're ussing direct sound in as the output the work is beign done by the onboard dsp of the soundcard anyway.

So the only quality you might gain is if the amp has a higher quality dsp then yorusoundcard, which really it should for the price increase :-) But who knows, i'd be curiose about the result, the problem for em though is i'm not noticing any processign noise as it is, so how can you get better then flawless? Least thats what my point of view is curently, listioning to 'better" coudl change that if it is better.

Make sure you're comparing base lines though, same speakers and volume levals, and no eq on amp or on the pc mp3 player.

[snw]

thanks for the response!
Originally posted by Antimon
[B]I've never seen an amp with a mp3 decoder unless it was incldued with a cd drive, in which case it's reading the data off the cd directly and has no input for it.

Well thsi is a long shot...but what if you tried hookingn the mp3 up to the intervideo decoder in graph edit?



I have a harman/kardon avr4000.

Here follows a scan from the manual: To take advantage of the AVR 4000's MP3 capabilities, simply connect the PCM output of a computer sound card able to feed the MP3 format to its digital output, or the PCM output of MP3 compatible CD or DVD players or of a portable MP3 player with a digital output, to either the rear panel Digital Inputs or the front panel Digital Inputs. When the digital MP3 signal is selected, the MP3 Bitstream Indikator will light, and the audio will begin playing. he AVR 4000 is only capable of playing sigals in the MP3 (MPEG 1 /Layer 3) format. It is not i not compatible with other computer audio codecs. the MP3 DSP mode found in the new AVR 4000 requires an MP3 SPDIF stream. resently, only a few units provide this but in the coming generations of motherboards and operatig system updates this will follow, since SPDIF is the standard for audio & video hardware.

As far as I understand this means the amp is able to decode a mp3 bitstream. Correct me if I'm wrong... I already tried hooking the mp3 file with intervideo decoder in graphedit ending up with only having a normal PCM output.

[Antimon]

eyah i agree with yoru interpritation of the manual, hmm, you're sure you're assing the audio over pspdif and not stereo out? yorusoudncard is set for "digital only" output corect?

i figured it is but to avoid the overlook, i figured i'd mention it.

hmm i'm not sure maybe only certian drivers/soundcards support it, and you'll have to wait.

it's oen fo thos ewhich came first games....the amp who can r ecieve the signal or the hardware thet can pass it.

[snw]

It works playing dts/ac3 so I think it is correct setup =)
I will try with another computer and soudcard some day, now I only tried with my notebook couse I have the sound system in another room... I also have a hollywood+ card i will try out... But thanks for all the help =)

[DSPguru]

it IS possible to playback mp3s thru spdif with amps that supports it. (avr-4000/avr-5000, for instance).

if you're thinking of burning mp3 into a cd (like MaTTeR did with DTS) - that's not advised.
the quality wouldn't be as good as audio-cd, and the playback time remains the same (74mins/80mins/etc'...).

as for using a digital soundcard SPDIF output in order to deliever mp3 packets to your amplifier - this is possible, and a very nice usage.
i recall reading a modified source-code of LiVid that delivered ac3 packets interleaved in a spdif streams (IEC-60958). modifying this code to deliever mp3 packets shouldn't be hard, and i bet someone done it already.
i suggest that you do some searches ;).

[LinneX]

Hey, I know that this thread is old, but it's the first thing I've found to that subject. Therefore I'm posting my question here. DSPguru said that there is (or might be) a source-code-mod of LiVid capable of rerouting MP3 Streams through SPDIF. Well LiVid is only available for Linux isn't it. Are there some Windows proggys available, too. (Buah Windows --- looser --- I know)

Thx for your help

Linne

[snw]

I'm wondering that too... Never got a chance to test it and I had forgot about it till now :p Would be nice to test it out! Mayby someone knows about some ds filter or some program capable of this. (I can't do any programming, if I could it would've been easier.. )
Thanx!

[zaphor]

I'm certenly inerested in this topic as well. I have a Harman/Kardon myself (AVR5500), but have never had the chance to test the DSP's MP3 decoder :-( I know I did a lot of search some year ago. I also was in contact with H/K, who told me, I should by their USB-dongle to hook into the DSP. Hmmph.

As previous posts says, there shouldn't be so much different than using the passthrouh mode of AC3 (Dolby Digtial) and DTS. The problem, though, is to get hold of the specifications for "MP3 over SPDIF" (from H/K?). I've search and I've searced, whithout finding anybody who has solved this issue.

I see the thread is somewhat old, so by this post I hope it wakes up again :rolleyes:

[Soulhunter]

Just to prove my lack of knowledge... :D


The new version of AC3Filter supports AC3/DTS/MPEG Audio SPDIF passthrough !!!

Ok, I already know about AC3/DTS passthrough...

But it has also MPEG audio passthrough !!!

Shouldnt this include MP3 passthrough ???


Bye