[Ipodlinux-devel] Memory (de-)allocation problem

[Jonathan C. R. <jon...@ba...>]

Hi Bernard et. al.,

As mentioned before on the mailing list, I am working on a play
queue/multi song buffer, and incorporating mp3 playback into podzilla. 
In the process, I have run into a problem with memory management.  After
coding and testing on the host (works great with libmad!) I
cross-compiled and installed the app on my iPod.  Upon initialisation I
allocate 16M for the buffer, but this fails on the iPod.  (Okay, I
probably need to allocate several blocks instead of one chunk, because
there is definately more than 20 M free, albeit not contiguous.)  I then
wrote a simple-minded programme to probe the maximum amount of
contiguous memory:

int main()
{
        int bytes = 1;
        char* buffer;

        while (buffer = (char*) malloc(bytes * sizeof(char))) {
                free(buffer);
                printf ("success with %d bytes\n", bytes);
                bytes <<=1;
        }

        return 1;
}

The app hangs after 64-512 bytes, with endless errors scrolling by on
the lcd display, too fast to read.  I am invoking the app via telnet
with the 2.4.24-ipod0 kernel. I have not tried it standalone. As there
are examples of malloc in existing code, I can only presume that there
is a problem with free(), or that I am missing the point entirely... (I
haven't coded plain c in a couple of years).

Anbody else seen this behaviour?  If not, any pointers as to how I can
debug it?  (Slowing down the console messages would be a start!)

A quick update on my progress: I have built a standalone libmad app with
console input (play/pause/quit) and with a modest (1 song) buffer (using
mmap).  This works fine on the iPod, except of course that it is not
100% real time... (a couple of tweaks in the configuration of libmad did
improve matters drastically though!  I still have hope...).  Otherwise,
I have built a circular buffer for multiple-track caching into
Podzilla.  Playback is incorporated into the main loop by decoding a
single frame in between each successive poll of the event loop.

As soon as I have sorted out the allocation problems and tidied up the
code a little, I will post my patches.

Thanks,
	Jonathan.

P.S. since I upgraded to the ipod0 kernel, I have not been able to ftp
-p 192.10.1.1 anymore.  Anyone know what's going on there?