Re: [alsa-devel] [PATCH 18/31] HDA patch_via.c: Add 48K sample rate limit for S/PDIF streams.
Li Bo: I'm not sure how changing the sample rate for SPDIF would have an effect of the SNR if you are only passing digital signals. I have had excellent measured results with the Via chipsets at all sample rates up to 192 KHz at 24 bits on the digital output. Perhaps you can explain how you measured the performance and that may explain your results. Normally if all of the data of the original file is present then any limit on SNR is a function of the DAC. If the data is not the same as the original file then there are more serious issues to be resolved, and it probably would not be useable with Dolby Digital or DTS.
Higher sample rates for digital content and digital interfaces are becoming more common and I think it would be a serious mistake to limit the performance of the platform.
Hi, Takashi
According to our HW test, S/PDIF at 48K sample rate has best SNR, so this
limit can make >S/PDIF work better.
Demian Martin Product Design Service 784 Cary Drive San Leandro, CA 94577 209 613 6990
Hi all,
I agree with the previous posts in this thread.
The use of > 48kHz sample rate is common use today, so if the hardware supports it, the driver should not disable it.
Since there are some users that successfully use SPDIF with > 48kHz, it cannot be a general hardware problem. If there's a general hardware problem, then it would never work for anyone.
If there are some codec chips/variants/versions, or even certain boards that have bad SPDIf signal performance, then we should black-list those bad chips/versions/boards, rather than disable the feature for everyone.
Also, as far as I understand, the worst thing that can happen when a "too high" sample rate is used: It will not work for some users on some hardware. That, I think, is acceptable (if no workaround / black-list can be created).
This would be different if there are other effects: If the high sample rate would cause some hardware-lock-up or similar, then it definitely needs to be disabled.
Regards,
On Tue, Oct 6, 2009 at 8:21 PM, Harald Welte laforge@gnumonks.org wrote:
Hi all,
I agree with the previous posts in this thread.
The use of > 48kHz sample rate is common use today, so if the hardware supports it, the driver should not disable it.
Since there are some users that successfully use SPDIF with > 48kHz, it cannot be a general hardware problem. If there's a general hardware problem, then it would never work for anyone.
If there are some codec chips/variants/versions, or even certain boards that have bad SPDIf signal performance, then we should black-list those bad chips/versions/boards, rather than disable the feature for everyone.
Also, as far as I understand, the worst thing that can happen when a "too high" sample rate is used: It will not work for some users on some hardware. That, I think, is acceptable (if no workaround / black-list can be created).
This would be different if there are other effects: If the high sample rate would cause some hardware-lock-up or similar, then it definitely needs to be disabled.
Regards,
- Harald Welte laforge@gnumonks.org http://laforge.gnumonks.org/
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Hi, All According to the discussion, this patch is canceled, thank you for suggestion.
participants (3)
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Demian Martin -
Harald Welte -
Li Bo