[SDL] SDL_Sound rewind - was SDL_mixer RWops

Keith Swyer ksswyer at adventus.com
Thu Jul 11 04:56:01 PDT 2002

well i could send the code, but essentially it's from the playwav.c example
with the loop structure changed a bit. it was able to continually loop, so i
just changed it a bit to set the number of loops. other than that, i am
using the paragui wrapper function to the physfs function that opens the mp3
from a zip file as RWops. and in the read_more_data function, after playing
once, if you have it set to loop, it calls the sound_rewind function, which
is returning an error for me.

but, if you would really like to see the code i can send it all....... but
here is just the clips of the read_more_data function and the function i use
to open the RWops

static int read_more_data(Sound_Sample *sample)
    if (done_flag)              /* probably a sigint; stop trying to read.
        decoded_bytes = 0;

    if (decoded_bytes > 0)      /* don't need more data; just return. */

        /* need more. See if there's more to be read... */
        decoded_bytes = Sound_Decode(sample);
        decoded_ptr = (unsigned char *)sample->buffer;
        return(read_more_data(sample));  /* handle loops conditions. */
    } /* if */

    /* No more to be read from stream, but we may want to loop the sample.

 //if looping is 0, then we either play once, or this is the final loop of
 //the sequence of loops. if -1, we always loop. it's placed second in the
 //if b/c we don't want the loop count decrement to continue past 0.
    if (looping == 0)
    else if (looping == -1){}

    /* we just need to point predecoded samples to the start of the buffer.
    if (predecode)
        decoded_bytes = sample->buffer_size;
        decoded_ptr = (unsigned char *)sample->buffer;
    } /* if */
        if (!Sound_Rewind(sample)){
         fprintf(stderr,"in reqind: %s", Sound_GetError());
    } /* else */

    assert(0);  /* shouldn't ever hit this point. */
} /* read_more_data */

//opening the mp3 - where rhythm_name is an mp3 in a zip file
SDL_RWops *ff = PG_FileArchive::OpenFileRWops(rhythm_name, PG_OPEN_READ);

----- Original Message -----
From: "Ryan C. Gordon" <icculus at clutteredmind.org>
To: <sdl at libsdl.org>
Sent: Wednesday, July 10, 2002 6:29 PM
Subject: Re: [SDL] SDL_Sound rewind - was SDL_mixer RWops

> > well, i've got my looping of audio working with sdl_sound, so i think
> > stick with it. however, i can only use a predecoded file to loop, there
> > problems when using the sound_rewind function. it can't. i'm using the
> > mpg123 lib and not the smpeg. i've looked into the code and the function
> > uses the SDL_RWops->seek method to rewind the Sound_SampleInternal->rw
> > SDL_RWops structure, but doesn't. i remember reading somewhere that this
> > be avoided by wrapping it in some sort of buffering SDL_RWops..... but
> > not sure how to do this....can anyone help please .
> The buffering RWops was never written, since it's roughly equivalent to
> predecoding. That being said, Sound_Rewind() works here with MPGLIB.
> What type of RWops do you have? Can we see the code?
> (We should also move this discussion to the SDL_sound mailing list: blank
> email to sdlsound-subscribe at icculus.org to get on that list.)
> --ryan.
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