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On 05/28/2011 12:50 PM, Alan Mackenzie wrote: |
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> Hi, Gentoo. |
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> |
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> It occurred to me the other day that I am clueless about how a sound |
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> card works. How do the data get into it? Does the sound card use an |
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> interrupt to ask for more data? |
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The data is placed in RAM. The card reads it from there using a DMA |
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operation. You can read about it here: |
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http://en.wikipedia.org/wiki/Direct_memory_access |
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> What form do the data take? |
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It's raw data, and its form depends on what the card is expecting. What |
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the card is expecting is programmable by the card's driver. |
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> Say I feed an mp3 through the card. Does |
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> the Athlon do the decompression, or does the sound card do it? |
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The MP3 is decoded by your CPU (by software like libmad, xine, |
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gstreamer, etc.) The decoded data is send to the driver, the driver |
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applies any needed conversions to it (according to what the card |
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expects), and then places it in RAM so the card can get it by means of DMA. |
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> Last of all, is there a command line program which can play a CD by |
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> feeding its data into the sound card? |
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Today this works the same playing any other audio. The fact that audio |
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in this case comes from a CD doesn't matter. An application reads the |
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audio from the CD, sends it to the driver, and from there it gets to the |
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sound card. |
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