On Mon, 2008-09-01 13:33:28 -0700, William Estrada MrUmunhum@popdial.com wrote:

Jan-Benedict Glaw wrote:

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On Mon, 2008-09-01 13:19:54 -0700, William Estrada MrUmunhum@popdial.com wrote:

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I am trying to use GDB with my ALSA program. I wish to display (print) a handle for an snd_pcm_t pointer. I am getting the following error:

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(gdb) p Device $9 = (snd_pcm_t *) 0x92be458 (gdb) p *Device $10 = <incomplete type>

How do I display the snd_pcm_t structure?

My guess is that this pointer is simply uninitialized. Did you check that it was properly prepared?

Yes, the device is opened. Is that what you mean??

Partially. But I misread your log, too. Seems that gdb failed to figure out how snd_pcm_t is actually defined. You'd try casting it to struct _snd_pcm * if the type information got lost somewhere. (You'd check the later by examining the `readelf -wi' output for your binary or library you're hacking on.)

MfG, JBG

Jan,

I have several programs that use the ALSA interface, most work the way they are supposed to. The one that require real time record and then play back are not working the way I want them to, There is a 4.09 second delay in the read interrupt. I think it is because the period value of the handle is not being saved correctly? So I wrote a test program to try and debug my problem. It would be helpful if these structures where not hidden.

I wrote a test program to try and debug my problem. From the output I can see that the data in the handle is getting messed up? I am not sure if this is another programming problem with in the display program (status.c)? The program works but the delay makes it unusable for my application. 'show_1' and 'show_2' are the same code just compiled differently.

The program(s) are here: http://64.124.13.3/_ALSA_ along with the source. The output <64.124.13.3/_ALSA_>of show_1 is:

$ ./show_1 14:37:52.266 Display_Audio_From_Function Device: 8c477b8 PCM Device name = 'default' PCM state = PREPARED access type = MMAP_NONINTERLEAV format = 'U8' (Unsigned 8 bit) subformat = 'STD' (Standard) channels = 1 rate = 8000 bps period time = 10000 us period size = 80 frame buffer time = 8192000 us buffer size = 65536 frames periods/buffer = 819 frames exact rate = 8000/1 bps significant bits = 8000 is batch = 0 is block transfer = 1 is double = 0 is half duplex = 0 is joint duplex = 0 can overrange = 0 can mmap = 1 can pause = 0 can resume = 1 can sync start = 1

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Device: 8c47b00 PCM Device name = 'default' PCM state = PREPARED access type = MMAP_NONINTERLEAV format = 'U8' (Unsigned 8 bit) subformat = 'STD' (Standard) channels = 1 rate = 8000 bps period time = 10000 us period size = 80 frame buffer time = 8192000 us buffer size = 65536 frames periods/buffer = 819 frames exact rate = 8000/1 bps significant bits = 8000 is batch = 0 is block transfer = 1 is double = 0 is half duplex = 0 is joint duplex = 0 can overrange = 0 can mmap = 1 can pause = 0 can resume = 1 can sync start = 1

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14:37:52.267 Voice On 14:37:52.267 Display_Audio_After_Function_Return Label: In, Device: 8c477b8 PCM Device name = 'default' PCM state = PREPARED access type = (null) format = 'FLOAT_LE' (Float 32 bit Little Endian) subformat = 'STD' (Standard) channels = 0 rate = 0 bps period time = -1081229612 us period size = 80 frame buffer time = 0 us buffer size = 0 frames periods/buffer = -1081229612 frames exact rate = 0/-1081229612 bps significant bits = 0 is batch = 0 is block transfer = 1 is double = 0 is half duplex = 0 is joint duplex = 0 can overrange = 0 can mmap = 0 can pause = 0 can resume = 1 can sync start = 1

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Label: Out, Device: 8c47b00 PCM Device name = 'default' PCM state = PREPARED access type = (null) format = 'FLOAT_LE' (Float 32 bit Little Endian) subformat = 'STD' (Standard) channels = 0 rate = 0 bps period time = -1081229612 us period size = 80 frame buffer time = 0 us buffer size = 0 frames periods/buffer = -1081229612 frames exact rate = 0/-1081229612 bps significant bits = 0 is batch = 0 is block transfer = 1 is double = 0 is half duplex = 0 is joint duplex = 0 can overrange = 0 can mmap = 0 can pause = 0 can resume = 1 can sync start = 1

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14:37:52.284 Starting Callback 14:37:52.284 Sleep 5 14:37:56.380 Enter Callback Label: Callback, Device: 8c477b8 PCM Device name = 'default' PCM state = RUNNING access type = (null) format = 'FLOAT_LE' (Float 32 bit Little Endian) subformat = 'STD' (Standard) channels = 0 rate = 0 bps period time = -1081230956 us period size = 80 frame buffer time = 0 us buffer size = 0 frames periods/buffer = -1081230956 frames exact rate = 0/-1081230956 bps significant bits = 0 is batch = 0 is block transfer = 1 is double = 0 is half duplex = 0 is joint duplex = 0 can overrange = 0 can mmap = 0 can pause = 0 can resume = 1 can sync start = 1

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14:37:56.381 Audio Ready: 32768 14:37:56.381 Voice 1 14:38:00.479 Exit Callback 14:38:00.479 Voice off 14:38:05.486 Exiting

If you have any ideas I would like to hear them.

Thanks again for your time.

Jan-Benedict Glaw wrote:

On Mon, 2008-09-01 23:13:26 +0200, Jan-Benedict Glaw jbglaw@lug-owl.de wrote:

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On Mon, 2008-09-01 13:33:28 -0700, William Estrada MrUmunhum@popdial.com wrote:

...

Jan-Benedict Glaw wrote:

...

On Mon, 2008-09-01 13:19:54 -0700, William Estrada MrUmunhum@popdial.com wrote:

...

I am trying to use GDB with my ALSA program. I wish to display (print) a handle for an snd_pcm_t pointer. I am getting the following error:

...

(gdb) p Device $9 = (snd_pcm_t *) 0x92be458 (gdb) p *Device $10 = <incomplete type>

How do I display the snd_pcm_t structure?

So... Looking at it, snd_pcm_t is willfully specified as a hidden struct, the real definition is only used where *really* needed, that is: inside libasound2. It's in pcm_local.h, to not allow an arbitrary user to easily fiddle with the lib's internal state.

As you want to peek into it, I guess you're facing a problem somewhere. It would probably help if you describe your actual problem.

MfG, JBG