[MPlayer-users] dtswav over SP/DIF does not work :-(

Sergey Melikhov melihov at yahoo.com
Mon Jan 24 02:05:01 CET 2005


I'm a long-time  mplayer user, and since I'm  writing
to this list for the first time, I'd like to say my
big "thank you" to the developers and supporters....

Well, I realized I'm  missing one thing in mplayer,
and that makes me to manually insert CDs into the DVD
player, instead of playing the music off the  hard
drive of my Linux box, as I prefer to do.

I searched archives of this list, and found a
discussion  exactly year ago, but I seen no practical
outcome in that discussion, so I decided to post a
question here.

The story:

Recently I set up a "home theater" at home (5.1
surround sound, driven by a Onkyo 602 receiver). As
the first thing, I connected my Linux box via coaxial
SPDIF cable to the receiver, configured my CM8738
card, and mplayer happily started sending PCM over the
digital connection.
That eliminated some noise, and overall quality of
sound has increased.  

Next thing I discovered, was music in DTS format on
CDs. I hardly can listen to regular CDs now, surround
sound is so impressive. My DVD player plays DTS CDs,
sends DTS to the receiver, and receiver reports that
it gets DTS. Works. 

Now if contents of the CDs are copied to the hard
drive, you get a bunch of WAV files. Which I
understand are DTS incapsulated in WAV, or DTSWAV

I got mplayer 1.0pre6a, configured it with
--enable-libdts and fed a DTSWAV file to it. Mplayer
started playing the file, but in stereo. It produced
PCM and sent that PCM to my receiver, as if the file
a usual MP3. 

Here's how it recognizes the file:

[demux_audio] DTS audio in wav, 14 bit, LE
demux_audio: audio data 0x2C - 0x6FD02C  
Audio file detected.

Then I tried digital pass-through option (-ac hwdts). 
Here the whole thing breaks:

 [demux_audio] DTS audio in wav, 14 bit, LE
demux_audio: audio data 0x2C - 0x6FD02C  
Audio file detected.
Forced audio codec: hwdts
Opening audio decoder: [hwac3] AC3/DTS pass-through
dec_audio: Allocating 8192 bytes for input buffer.
dec_audio: Allocating 16384 + 65536 = 81920 bytes for
output buffer.
No accelerated IMDCT transform found
hwac3: switched to AC3, 384000 bps, 48000 Hz
a52: CRC check failed!  
AUDIO: 48000 Hz, 2 ch, 16 bit (0x400), ratio:
48000->192000 (384.0 kbit)
Selected audio codec: [hwdts] afm:hwac3 (DTS through
Freeing 0 unused video chunks.
Starting playback...
a52: CRC check failed!  
a52: CRC check failed!  
a52: CRC check failed!  
a52: CRC check f

First thing I see here, is the 48000Hz frequency. I
guess that these  files are in 44100Hz since they came
from a CD. This is a valid option for DTS. 

Can 44100 be supported? 

(please note that AC3 from movies is sent to the
receiver correctly with -ac hwac3 option, and works
quite well).

I was researching Internet for this matter, and could
find very little experience there. I came across of a
Windows guys' discussion  about the same kind of set
They could do it, and their major problem was not
software, but hardware.
Someone mentioned that common sound cards used are
"not bitperfect", and corrupt DTS flow. Someone said
CM8738 was in fact "bitperfect". I don't know what to
think here. AC3 is being played fine, I don't know if
DTS is less tolerant format than AC3 or not.. I still
have a hope here that this can be resolved, and
mplayer will shine in this area as well as it does
everywhere else. As the last resort I could buy a 
different sound card. But at this point it looks like
mplayer has problem. If this problem can be  resolved,
then hardware problem can be  looked into, if any. 

Thanks to those who read this far. Thanks for advice,
if any can be given, other than switching to Windows.


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