[mythtv-users] "Do you really need a discrete audio card ?"

[Emmanuel]

Andre a écrit :
> On 25 Nov 2010, at 11:35, James Courtier-Dutton wrote:
>
>   
>> On 22 November 2010 21:41, Christopher X. Candreva <chris at westnet.com> wrote:
>>     
>>> Tech Report has release an interesting review, comparing the Asus Xonar
>>> cards to the common built-in Realtek chips, with the low-end ($29) Xonar
>>> comming out as a worthwhile upgrade.
>>>
>>> Aside from the article being interesting, it made me wondering if switching
>>> audio cards would help with the "WriteAudio: buffer underrun" problems I
>>> have with untranscoded content, which hasn't gone away with 0.24
>>>
>>>       
>> Having worked on ALSA for many years, I agree that on-board sound
>> cards are considerably worse that even cheap PCI ones.
>> The worst offenders are laptop ones though.
>> While sound output is not so much a problem, the real problem comes
>> with the "mic" input when using a VoIP product like skype.
>> While developing a VoIP app, we were adding noise cancellation
>> features to the software.
>> I had a discrete PCI sound card, and the Mic input had something like
>> 12dB (a lot) better S/N ratio than a laptop mic input.
>> I also talked to some sound hardware engineers at EMU, and they told
>> me the problems with laptop mics are all solvable, but require the
>> addition of about 3 extra capacitors/resistors to the motherboard, and
>> the motherboard manufacturer prefers to save a few pence and not
>> include those components.
>>
>> It is true that you only need to spend money on the Analogue
>> components in your audio system to get good sound.
>> 1) DAC
>> 2) ADC
>> 3) The AMP with the analogue speaker outputs.
>> 4) Speakers/Headphones.
>>
>> So, a graphics card with audio over HDMI will sound identical to any
>> other graphics card with HDMI.
>> Just like, for less than 4 Meters, any v1.3 HDMI cable will work. No
>> need to buy expensive ones because it is digital.
>> You might have to be more careful with long HDMI cables, due to
>> electrical transmission reasons. Much like Ethernet cables, although
>> digital in nature have limits on how long you can make the cables.
>> HDMI is sort of equivalent to a 10Gbps copper Ethernet cable if one
>> existed.
>>
>> I would prefer it if the speaker industry moved to speakers with
>> direct digital inputs, so the speaker unit would have a SPDIF or Audio
>> over Ethernet input, and the speaker itself have the amp and speaker
>> drive unit all in one. One could even move of a standard of something
>> like ethernet audio over mains to get the sound to the speakers and
>> cut down on cables used.
>> Then, one could buy cheap everything else because it would be digital,
>> and the only component that would make any difference to the sound
>> output would be the speaker unit itself. You could then make the
>> speaker perform better because you could implement feedback mechanisms
>> so the circuit could detect where the speaker cone is at any one time
>> and modify the drive to better match the input digital PCM signal and
>> further reduce distortion.
>>     
>
> Hear Hear,
>
> There are many monitoring speakers used in the TV industry like this, usually they have an XLR socket for line level balanced audio and all amplification is inside the speaker, one really nice side effect is for stereo you buy 2 for surround you buy 5 or 7, having 5 (or 7) identical speakers makes surround really great. I've recently seen some versions that accept AES digital audio and you can usually feed co-axial spdif into an AES port with an adaptor and the speaker will play it correctly. Generally these speakers are quite small but they seem to manage some impressive bass due to the close coupled and matched amplifier and speaker.
>
> So you could go buy some Genelec or Fostek monitor speakers and get exactly what you desire, will cost an arm and several legs though ;-)
>   
One thing though: digital is OK all the way to the speaker as it wont be 
degraded but I would not use analog (especially line level audio) over 
long cables, as it would be all kinds of noise.
</dreaming on>
But the perfect word would be: several speakers with onboard DAC and amp 
all plugged to the mains and get their audio from them. Probably a sync 
problem has to be solved but well it sounds doable.

</dreaming off> ;-)