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PCM2902b Annoyance

Mitchell Solomon
Intellectual 330 points

Other Parts Discussed in Thread: PCM2902

i know there is no way (execpt at rom mask level) to change the USB terminal type from 0x0201 (microphone) to something better for my application... like (0x701) Radio Receiver, heck even a line in would be better
0x201 causes windows vista and windows 7, to make it the default recoding device on initial plugin

terminal type 0x0201 doesnt even make sense when somone would use the SPDIF in, no mics are SPDIF :)

I would also love to disable the output interface... so that doesnt even show up.... (and take over playback device on WINDOWS on inital plugin)

im basicly using the 2902 as INPUT ONLY for hd radio receiver (after setting up windows, it does work great)

Question... it doesnt seem documented, two pins SEL0 and SEL1 (what do they do?, if anything)... would be cool if could have it set some defaults... how about sel0 disables OUT ENDPOINT TERMINAL

oh it would be great if this IC had a full eepom (with not just VID/PID, but other settings for dsabling output or input(some people only use it for speakers!)

oh another thing, on XP, the device enumerates with NO level or mute control avail... for the input terminal, very odd...

thanks!

mitch

  • 0
    TI__Expert 5555 points

    Hello Mitchell,

    My name is Dafydd Roche, I'm on the product definition team for next gen audio converters.

    The PCM2902 was before my time, however, I just wanted to say that I really appreciate your feedback, and ideas for next gen products.

    I will forward this question to the development team, and see what feedback I can get.

    Thanks again

    Dafydd

     

  • 0 in reply to Dafydd Roche
    Intellectual 330 points

    GREAT,

    im glad someone finnally notest my post... im moving forward with my project
    and it is a ISSUE, that the terminal type is 0x0201= Microphone

    causes windows 7 to think its a microphone, when im using it basicly as line in
    (actually in my case a FM Radio terminal type 0x710)

    (man i wish it was optional eeprom, with settings like this... heck id take 0x200 or 0x0603)

  • 0 in reply to Mitchell Solomon
    Intellectual 330 points

    bump...

     

    not to mention, that on windows 7, the device is WAAAY too loud, prob windows 7, since it thinks its input is a microphone, is applying some kind of boost

     

    mitch

  • 0 in reply to Mitchell Solomon
    TI__Expert 4160 points

    Mitch,

    When a microphone is attached to a PC via USB, the audio packets traversing the USB are typically PCM, meaning that audio scaling should have happened _before_ the A/D converstion and the samples are sent by the device.  Sixteen-bit samples from a microphone should thus range between 0x7fff (+32767) and 0x8000 (-32768), for maximum SNR, just like samples from Line In.  So, I don't understand why you think that 'Mic In' would produce significant level differences from 'Line In'.  Can you explain?

    Thanks,

    Frank  

  • 0 in reply to Frank Minich
    Intellectual 330 points

    your right, i dont know for sure...

    but what i do know is that windows 7, sees the TERMINAL TYPE as microphone, and ITS INCREADBLY TOO LOUD!!!!
    basically making the PCM29xx series almost useless on Windows 7, i have to lower volume to 3 to at least have no distortion

    its possible that windows 7 audio system is applying a BOOST because it thinks its a microphone..
    but there really is no way to test this is the PC29xx series has the TERMINAL TYPE HARD CODED into the descriptor

    ok, even if its not an issue with level in the IC, the annoying factor that its TERMINAL TYPE is hard coded to microphone
    has other side effect in windows.... if we could change it to say LINE-IN, windows would chose a better icon and description
    since in a lot of cases the PCM29xx isnt connected to a microphone, it would be nice to have this option

    EVERYDAY , i search the web looking for a better solution then the 29xx series, due to thier inherent limitations

     

  • 0 in reply to Mitchell Solomon
    TI__Expert 4160 points

    Mitch,

    Do you see the problem when you connect to a Win XP PC?  That is, is the problem Win7-specific?

    Which PCM29xx part are you using?  Is it possible that your microphone is overdriving its input?

    Can you look at the USB traffic (i.e., using a sniffer)?

    I still find it _extremely_ difficult to believe that the problem is related to LineIn/MicIn.  What comes in over USB should already have been normalized prior-to A/D.

    Regards,

    Frank

  • 0 in reply to Frank Minich
    TI__Expert 4160 points

    Hold the phone ... another customer has complained in regard to Win7 and has provided their implementation, so we're taking a look at it.

  • 0 in reply to Frank Minich
    Intellectual 330 points

    i know this, the ISSUE is not in VISTA!! the volume can be nicely set at 50

     

    glad you got some info... its so annoying, i get complaints, that my products audio is all destorted... its becuase of the level > 4


    what im thinking its because the terminal type is MICROPHONE, windows 7, is applying a internal BOOST to the audio
    I could be a problem with windows 7, but i would NOT assume that, if i was a mfg i would do EVERYTHING possible
    to see if my product is the issue, or if i can adapt to Win7, and if not, then bring up the issue with Microsoft...
    I have tried 3 differnt products, but all have the pcm29xx product inside, they all have this same problem...

     

     

  • 0 in reply to Mitchell Solomon
    Prodigy 10 points

    I can confirm that this is a Windows 7 issue.

    The PCM2902 product used on the Window XP platform was, in my case, just the opposite.  The record level needed to be at 100% and even then was a bit on the low side.  

     

  • 0 in reply to Mike Long
    Prodigy 10 points

    It's a Windows 7 only issue. As  PCM290x has no input volume, windows 7 "provides" one. In digital form.

    The samples are just overscaled to produce the gain. To get a satisfactory sound quality, you have to set the recording levet to about 3%.

    Windows 7 also assumes it is a mono input. Windows 7 just assumes too much...

    Has anybody tried this part on Windows x64? I seems to me it doesn't work. At least with the windows native drivers (usbaudio.sys).

  • 0 in reply to Antonio Rohrbacher
    TI__Expert 5555 points

    Hello Gents,

    this is a known issue with Win7, which we've been working with key customers to understand in the last few months.

    The PCM290x codecs identify themselves to an operating system as having microphone inputs. In previous operating systems, there was no differentiation in the signal processing between a product identifying itself as a line in or a microphone input. As mentioned in this thread, XP has no issues, OSX has no issues, Ubuntu has no issues.

    However, It appears that when Win7 differentiates the way it treats a product based on how it's USB descriptors have been set.

    Any products identifying themselves as USB Microphone inputs without programmable gain controls get treated with additional digital gain, within Win7.

    We are looking at different ways to approach this problem, as will communicate through the community, and the product folders on www.ti.com when we have something that's ready to go public.

    Thanks again

    Dafydd Roche

     

     

     

  • 0 in reply to Antonio Rohrbacher
    Expert 2066 points

    Antonio Rohrbacher said:

    The samples are just overscaled to produce the gain. To get a satisfactory sound quality, you have to set the recording levet to about 3%.

    Right-click the number and it will give you the option for decibels instead of percent.  Set it as close as possible to 0 dB to get it back to normal operation (I think the percent scale is different in Vista and 7).  It shows up as +30 dB by default, which is causing customers to return our products as "too noisy", and not just with the TI PCM chips.  I talked to a Microsoft developer who actually referred to this default value as a "bug", but didn't seem to think it would be fixed any time soon.

    Windows 7 also assumes it is a mono input. Windows 7 just assumes too much...

    Has anybody tried this part on Windows x64? I seems to me it doesn't work. At least with the windows native drivers (usbaudio.sys).

    Same problem here with Windows 7 64-bit, too.  If a device exposes both a 1 channel and 2 channel configuration, Windows 7 seems to choose the 1 channel by default.  Again, people are unaware that they can change this in Recording Properties, so they assume "this product isn't compatible with Windows 7" and return it.

    Here's a post about both issues by a different Microsoft employee, calling it a "known issue":

    http://www.freelists.org/post/wdmaudiodev/Change-default-sound-format-with-an-inf-File-in-Win7,4