Hi Martin,

First- sample rate

Even though the documents claim that it will play at 176.4 KHz and 192KHz whenever I play a file at these rates it down converts to ½ the rate (88200 and 96000). I tested this with the ICE1724HT (Juli@) which has almost the same core, I never could get 176.4KHz at the SPDIF output. I confirmed that the ICE1724 will play the file at 176.4KHz in Windows so its not a hardware limitation. I tried to do the same with the VT1708 (on a Via CX700 chipset) and the Windows driver wouldn’t let me at anything other than 48000.

I spent a few days on this issue and confirm that ICE1724HT cannot output 176.4kHz from its internal SPDIF transmitter, WHEN clocked by its internal clock circuits. A scope hooked to corresponding pins/outputs revealed the following:

All I2S lines output correct 176.4kHz signal, i.e. D/A codecs receive proper signal.

However, I did not find a way to force ICE1724 to output 176.4kHz, it always drops to 88.2kHz, no matter what MT01/MT02 combination is. The same happens with windows drivers of my Prodigy 192. The sequence is: 44.1, 48, 88.2, 96, 88.2, 192

I have not seen any manufacturer of Envy-based cards revealing this deficiency. The "preliminary" datasheet we all use mentions only that the chip forces the 128x mode when switched to 176.4kHz. I believe the output of 88.2kHz is an undocumented feature or perhaps even a bug of the chip.

Juli is a card whose manufacturer may be aware of the problem. It is not clocked by ICE1724 internal clocks fed by the two crystals. Instead, the crystals also provide signal to external circuits generating clock signals of required frequency, feeding the chip in slave mode. The circuitry is controlled by ice1724 GPIOs.

This way the ICE1724 is not aware of its clocking frequency and cannot thus mis-configure its SPDIF transmitter. The windows driver does output proper 176.4kHz.

I am working on Juli driver and have been analyzing this beast for a few nights. The special clocking is already working at home :)

Second, the only way I can get the 24 bit files out in a form that the card can play is to pass them through dmix. But I need to reconfigure dmix for each sample rate. And I’m not convinced that it isn’t resampling twice, both at the input and the output. Or how to configure the buffers etc. to prevent underruns even when the only conversion is to pass a 24 bit file to the card.

ICE cards use 32bits format. Try aplay -v -D plughw:0 24bit.wav and you will see the conversion to 32 bits done by the plug plugin, no dmix involved.

I’m trying to build a high quality music server that will pass the files to either the internal or an external DAC at the bit depth and sample rate they were recorded at. I have tried to understand the various plugs and settings but it seems they are all focused on mixing various streams. I want to send the files unmixed to the output. I can’t figure out what set of plugs and settings in asound.conf would enable this.

Check the plug plugin.

Regards,

Pavel Hofman. -----------------

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