Hi,
I have a Gigabyte GA-7VA motherboard, equiped VIA KT400/VT8235 chipset
with an Athlon XP 1900+. Its AC97 codec is the Realtek ALC650, capable of
SPDIF in/out and 6-channel output.
My goal is to decode the AC-3 SPDIF signal from my DVD and to play it
using the PC. By using alsamixer for configuring the ALC650 to read
SPDIF in, and a simple spdifac3 program I did to extract AC-3
from SPDIF stream, I can almost get what I want:
arecord -f dat -t raw | spdifac3 | ac3dec -D sur51
The problem is that I get CRC frame errors. Here is a list of what I
already did:
1 - Install kernel 2.4.18 with 'Low latency' and 'Preempitve Kernel'
patches. HZ = 100
2 - Install alsa 0.9.6. I modified the ALC650 code to enable
'Extension register Write Enable' (GPIO Status:15), and to add
different SPDIF input related controls.
3 - For testing purposes, create a ram disk to avoid IDE interrupts
(/mnt/ramd)
4 - As root, I did a small program (setrtsched) where I set the schedule
policy to SCHED_RR and schedule priority to 99. Then I also use nice
to increase the priority:
setrtsched nice -n -20 arecord -f dat -t raw -d 20 > /mnt/ramd/bitstream
5 - Tried increasing the buffer size to include several period_size
interrupts.
After all this, I still loose data reading SPDIF. From time to time, I
loose 1 sample (4 bytes) which generates the 'CRC frame error' in ac3dec
and the umpleasant 'tak' in my speakers.
I would really appreciate if somebody give me some hint and/or
information. I attach below some information.
Thanks a lot
Alejandro
[EMAIL PROTECTED] linux-2.4.18]# /sbin/lsmod
Module Size Used by Tainted: P
nls_iso8859-1 3548 0 (autoclean)
nls_cp437 5148 0 (autoclean)
vfat 12892 0 (autoclean)
fat 39576 0 (autoclean) [vfat]
sr_mod 17848 0 (autoclean)
snd-usb-audio 54304 0 (unused)
snd-via82xx 17248 0
snd-pcm 86240 0 [snd-usb-audio snd-via82xx]
snd-timer 20612 0 [snd-pcm]
snd-page-alloc 10260 0 [snd-via82xx snd-pcm]
snd-mpu401-uart 5456 0 [snd-via82xx]
snd-rawmidi 19584 0 [snd-usb-audio snd-mpu401-uart]
snd-seq-device 6220 0 [snd-rawmidi]
snd-ac97-codec 50680 0 [snd-via82xx]
snd 44740 0 [snd-usb-audio snd-via82xx snd-pcm
snd-timer snd-mpu401-uart snd-rawmidi snd-seq-device snd-ac97-codec]
autofs 13604 1 (autoclean)
adiusbadsl 103424 1
ipt_REJECT 3800 11 (autoclean)
ipt_MASQUERADE 2328 1 (autoclean)
iptable_nat 19864 1 (autoclean) [ipt_MASQUERADE]
ip_conntrack 21720 1 (autoclean) [ipt_MASQUERADE iptable_nat]
iptable_filter 2412 1 (autoclean)
ip_tables 14840 6 [ipt_REJECT ipt_MASQUERADE iptable_nat
iptable_filter]
ide-scsi 10384 0
scsi_mod 105892 2 [sr_mod ide-scsi]
ide-cd 32884 0
cdrom 33216 0 [sr_mod ide-cd]
audio 44436 0
soundcore 6692 2 [snd audio]
mousedev 5556 1
keybdev 2880 0 (unused)
hid 21732 0 (unused)
input 5760 0 [mousedev keybdev hid]
usb-uhci 26956 0 (unused)
usbcore 69024 1 [snd-usb-audio adiusbadsl audio hid usb-uhci]
ext3 70752 2
jbd 52400 2 [ext3]
[EMAIL PROTECTED] linux-2.4.18]# cat /proc/asound/V8235/ac97#0
0-0/0: Avance Logic ALC650 rev 0
Capabilities :
DAC resolution : 20-bit
ADC resolution : 18-bit
3D enhancement : Realtek 3D Stereo Enhancement
Current setup
Mic gain : +0dB [+0dB]
POP path : pre 3D
Sim. stereo : off
3D enhancement : off
Loudness : off
Mono output : MIX
Mic select : Mic1
ADC/DAC loopback : off
Extended ID : codec=0 rev=1 LDAC SDAC CDAC DSA=0 SPDIF DRA VRA
Extended status : SPCV LDAC SDAC CDAC SPDIF=res SPDIF VRA
PCM front DAC : 48000Hz
PCM Surr DAC : 48000Hz
PCM LFE DAC : 48000Hz
PCM ADC : 48000Hz
SPDIF Control : Consumer PCM Copyright Category=0x2 Generation=1 Rate=48kHz
[EMAIL PROTECTED] linux-2.4.18]# cat /proc/asound/V8235/ac97#0regs
0:00 = 5980
0:02 = 1111
0:04 = 0000
0:06 = 801f
0:08 = 0000
0:0a = 801e
0:0c = 801f
0:0e = 0008
0:10 = 9f1f
0:12 = 8707
0:14 = 9f1f
0:16 = 9f1f
0:18 = 1010
0:1a = 0000
0:1c = 0a0a
0:1e = 0000
0:20 = 0000
0:22 = 0003
0:24 = 0000
0:26 = 000f
0:28 = 05c7
0:2a = 05f5
0:2c = bb80
0:2e = bb80
0:30 = bb80
0:32 = bb80
0:34 = 0000
0:36 = 0000
0:38 = 1010
0:3a = 2824
0:3c = 0000
0:3e = 0000
0:40 = 0000
0:42 = 0000
0:44 = 0000
0:46 = 0000
0:48 = 0000
0:4a = 0000
0:4c = 0000
0:4e = 0000
0:50 = 0000
0:52 = 0000
0:54 = 0000
0:56 = 0000
0:58 = 0000
0:5a = 0000
0:5c = 0000
0:5e = 0000
0:60 = 1902
0:62 = 4200
0:64 = 0808
0:66 = 0808
0:68 = 0000
0:6a = 0800
0:6c = 0000
0:6e = 0014
0:70 = 0211
0:72 = 00a0
0:74 = 0043
0:76 = 0000
0:78 = 8003
0:7a = 57c7
0:7c = 414c
0:7e = 4720
-------------------------------------------------------
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