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Topic: I cannot get full bitrate with DVD-A or SACD streams; why? (Read 13502 times) previous topic - next topic
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I cannot get full bitrate with DVD-A or SACD streams; why?

Hello all,

Recently I have faced with an issue, I explain here.

I have got some SACD Raw ISO image files and some DVD-Audio ISO files and play them with foobar, the bitrate for SACD files is written for nearly 17Mbps but I convert it to PCM (Multi-stage, Floating Point) with sample rate of 174.6 kbps, I think due to this thing (lowering sample rate for PCM) won't give me the full bitrate so, the bitrate is near about 9Mbps, but the issue is with DVD-Audio image files, they are 24-bit/96kHz, while my audio system support for 24/192 again I can not get the full 13.8Mbps bitrate of MLP codec (6 ch) even I listen in multi-channel form, again I get a Variable bitrate with average of 8.5Mbps.

I wanted to know is there any specific reason for this? I think there is a problem with sample rate, because if we calculate bitrate with sample rate of 88.2kHz everything will be in right place, but why bitrate is variable in the first place?

Thanks,
Pink

I cannot get full bitrate with DVD-A or SACD streams; why?

Reply #1 –
I'm not sure I understand, but you mean that you're using 174.6 kHz sample rate and 24 bit per sample stereo right?

I cannot get full bitrate with DVD-A or SACD streams; why?

Reply #2 –
I think you're assuming that the audio will use the full data rate all the time? MLP is variable just like FLAC (it uses lossless compression as far as I'm aware) so I wouldn't expect to see the maximum bitrate all the time.

I cannot get full bitrate with DVD-A or SACD streams; why?

Reply #3 –
Stereo or multi-channel, no matter.
FLAC is not variable, I think; but the difference between the full bitrate and the real-time bitrate that foobar shows me is too much (more than 4-5Mbps).

I cannot get full bitrate with DVD-A or SACD streams; why?

Reply #4 –
Quote from: Pink123 on
FLAC is not variable, I think
Fortunately, you-think does not equal it-is. FLAC, like all lossless codecs, uses a variable bitrate—by definition, since otherwise one cannot achieve both losslessness and reduction in file size.

I cannot get full bitrate with DVD-A or SACD streams; why?

Reply #5 –
You'd be surprised how much space is saved by compression, ESPECIALLY in multi-channel stuff.  Sometimes when ripping 5.1 lossless movie tracks to FLAC, mine end up a lower overall bit rate than the lossy 1.5 Mbps DTS core tracks, while the whole DTS-HD Master plus DTS lossy core is usually well over 3500 kbps.

I cannot get full bitrate with DVD-A or SACD streams; why?

Reply #6 –
But reduction in file size by compressing lossless codec will not downgrade the quality, the compression is related to codec itself, make it harder to decode on very high settings, it does not affect quality.

I cannot get full bitrate with DVD-A or SACD streams; why?

Reply #7 –
Right...but what does this have to do with your comments before about thinking the reduction in bit rate is too much?

I cannot get full bitrate with DVD-A or SACD streams; why?

Reply #8 –
Quote from: ramicio on
Right...but what does this have to do with your comments before about thinking the reduction in bit rate is too much?


Yes, you are right, so, what's the reason for that? both SACD and DVD-Audio gives me that average bitrate, is it ok or what?

I cannot get full bitrate with DVD-A or SACD streams; why?

Reply #9 –
Quote from: Pink123 on
Quote from: ramicio on
Right...but what does this have to do with your comments before about thinking the reduction in bit rate is too much?


Yes, you are right, so, what's the reason for that? both SACD and DVD-Audio gives me that average bitrate, is it ok or what?


I don't understand the question.  What are you comparing exactly?

I cannot get full bitrate with DVD-A or SACD streams; why?

Reply #10 –
For uncompressed PCM, Bitrate = Samples Per Second x Bits Per Sample x  Number Of Channels

Lossless compression should compress the file to somewhere around 60% of it's original size (and around 60% of the original bitrate).  Actual compression ratio depends on the compresion format/algorithm and the program material.

Quote
... they are 24-bit/96kHz, while my audio system support for 24/192 again I can not get the full 13.8Mbps bitrate of MLP codec (6 ch) even I listen in multi-channel form, again I get a Variable bitrate with average of 8.5Mbps.
  ~62%...  Looks right to me!


P.S.
I dont know if that 60% rule-of-thumb holds for floating point.  I would guess that floating-point doesn't compress very well (losslessly) unless the floating-point was converted from an integer format.

I cannot get full bitrate with DVD-A or SACD streams; why?

Reply #11 –
Quote from: Pink123 on
Yes, you are right, so, what's the reason for that? both SACD and DVD-Audio gives me that average bitrate, is it ok or what?


It's just compression.  Any form of compression is going to be smaller than the raw thing.  Like DVDDoug said, stuff is usually compressed down to around 60%.  You still get the same exact info out that went in before compression, like a ZIP or RAR.
 

I cannot get full bitrate with DVD-A or SACD streams; why?

Reply #12 –
So, I get the full bitrate like before compression,
Thank you so much guys, I've got my answer.