[alsa-devel] Setting format to SND_PCM_FORMAT_MU_LAW does not let me apply hardware parameters
ghjeold_i_mwee at cox.net
Thu Jul 17 05:30:06 CEST 2008
Mitul Sen (misen) wrote:
> I am making some changes to the alsa-lib code and I have built alsa-lib. But I don't think its really picking up my changes. How can I make sure that my application uses the
modified library? I don't have to load any modules, do
I? I am sorry if this is too basic a question but I
couldn't find the info on a quick google search.
Basically what I want to know is what are the steps to
develop alsa-lib. This is what I did
> 1) Downloaded the source code
> 2) Configured the system using ./configure
> 3) Did a build using make
> 4) Did a "make install"
> Am I missing something here?
It looks correct. Do an ls -l /usr/lib/libasound*.
The file there should have the same timestamp as the
file in your build directory. If it doesn't, it didn't
install. You could just copy it over.
Make sure there is no other copy in /lib.
> Also regarding the original problem, when I run my program, the output of /proc/asound/card0/pcm0p/sub0/hw_params is
> access: MMAP_INTERLEAVED
> format: S16_LE
> subformat: STD
> channels: 2
> rate: 48000 (48000/1)
> period_size: 32
> buffer_size: 1024
> This is clearly not what it should be since the data access should be RW_NONINTERLEAVED, format should be MU_LAW, there is only one channel and rate is 8000. Which would mean that alsa assumes a different set of parameters (for mu law)from what the data actually is. Am I right in thinking this?
> Just got back after a long break and trying to pick up the threads again:-)
> Again, any help will be much appreciated.
Unless your changes changed the mu-law code to use your
card's mu-law decoder, they will still be the decoded
The best way to do this is to compile your program with
debugging enabled ( -ggdb -O0) and the alsa library
with debugging enabled. ./configure --help should
give you the option. Then move only the library to
/usr/lib and run your program as
gdb --args yourprogram yourargs . You can see the
info on how to run gdb in info gdb . With the
debugger you can step through the program and the
library to see where it is not working the way you
expected. But you don't want to leave it like that as
it is very inefficient.
If your code works for the mu-law, you could submit a
patch. Of course, you would have to check for the
functionality and branch to the old code if the card
doesn't support mu-law decoding.
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