view decoders/skeleton.c @ 474:c66080364dff

Most decoders now report total sample play time, now. Technically, this breaks binary compatibility with the 1.0 branch, since it extends the Sound_Sample struct, but most (all?) programs are just passing pointers allocated by SDL_sound around, and might be okay. Source-level compatibility is not broken...yet! :) --ryan. -------- Original Message -------- Subject: SDL_sound patch: Finding total length of time of sound file. Date: Sun, 26 Jan 2003 09:31:17 -0800 (PST) Hi Ryan, I am working with Eric Wing and helping him modify SDL_sound. AS part of our efforts in improving and enhancing SDL_sound, we like to submit this patch. We modified the codecs to find the total time of a sound file. Below is the explanation of the patch. The patch is appended as an attachment to this email. * MOTIVATION: We needed the ability to get the total play time of a sample (And we noticed that we're not the only ones). Since SDL_sound blocks direct access to the specific decoders, there is no way for a user to know this information short of decoding the whole thing. Because of this, we believe this will be a useful addition, even though the accuracy may not be perfect (subject to each decoder) or the information may not always be available. * CONTRIBUTORS: Wesley Leong (modified the majority of the codecs and verified the results) Eric Wing (showed everyone how to do modify codec, modified mikmod) Wang Lam (modified a handful of codecs, researched into specs and int overflow) Ahilan Anantha (modified a few codecs and helped with integer math) * GENERAL ISSUES: We chose the value to be milliseconds as an Sint32. Milliseconds because that's what Sound_Seek takes as a parameter and -1 to allow for instances/codecs where the value could not be determined. We are not sure if this is the final convention you want, so we are willing to work with you on this. We also expect the total_time field to be set on open and never again modified by SDL_sound. Users may access it directly much like the sample buffer and buffer_size. We thought about recomputing the time on DecodeAll, but since users may seek or decode small chunks first, not all the data may be there. So this is better done by the user. This may be good information to document. Currently, all the main codecs are implemented except for QuickTime.
author Ryan C. Gordon <icculus@icculus.org>
date Sat, 08 May 2004 08:19:50 +0000
parents fb519e6028e3
children 50bb9a6cebfe
line wrap: on
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/*
 * SDL_sound -- An abstract sound format decoding API.
 * Copyright (C) 2001  Ryan C. Gordon.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

/*
 * FMT decoder for SDL_sound.
 *
 * This driver handles FMT audio data. Blahblahblah... The author should
 *  have done a search and replace on "fmt" and "FMT" and changed this
 *  comment. This is the default comment in the skeleton decoder file...
 *
 * None of this code, even the parts that LOOK right, have been compiled,
 *  so you cut-and-paste at your own risk.
 *
 * Please see the file COPYING in the source's root directory.
 *
 *  This file written by Ryan C. Gordon. (icculus@clutteredmind.org)
 */

#error DO NOT COMPILE THIS.
#error  This is an example decoder skeleton.
#error  You should base your code on this file, and remove these error lines
#error  from your version.

#if HAVE_CONFIG_H
#  include <config.h>
#endif

#ifdef SOUND_SUPPORTS_FMT

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "SDL_sound.h"

#define __SDL_SOUND_INTERNAL__
#include "SDL_sound_internal.h"

static int FMT_init(void);
static void FMT_quit(void);
static int FMT_open(Sound_Sample *sample, const char *ext);
static void FMT_close(Sound_Sample *sample);
static Uint32 FMT_read(Sound_Sample *sample);
static int FMT_rewind(Sound_Sample *sample);
static int FMT_seek(Sound_Sample *sample, Uint32 ms);

static const char *extensions_fmt[] = { "FMT", NULL };
const Sound_DecoderFunctions __Sound_DecoderFunctions_FMT =
{
    {
        extensions_fmt,
        "FMT audio format description",
        "Ryan C. Gordon <icculus@clutteredmind.org>",
        "http://www.icculus.org/SDL_sound/"
    },

    FMT_init,       /*   init() method */
    FMT_quit,       /*   quit() method */
    FMT_open,       /*   open() method */
    FMT_close,      /*  close() method */
    FMT_read,       /*   read() method */
    FMT_rewind,     /* rewind() method */
    FMT_seek        /*   seek() method */
};


static int FMT_init(void)
{
    /* do any global decoder/library initialization you need here. */

    return(1);  /* initialization successful. */
} /* FMT_init */


static void FMT_quit(void)
{
    /* do any global decoder/library cleanup you need here. */
} /* FMT_quit */


static int FMT_open(Sound_Sample *sample, const char *ext)
{
    Sound_SampleInternal *internal = (Sound_SampleInternal *) sample->opaque;
    SDL_RWops *rw = internal->rw;

    if (can NOT accept the data)
        BAIL_MACRO("FMT: expected X, got Y.", 0);

    SNDDBG(("FMT: Accepting data stream.\n"));
    set up sample->actual;
    sample->flags = SOUND_SAMPLEFLAG_NONE;
    return(1); /* we'll handle this data. */
} /* FMT_open */


static void FMT_close(Sound_Sample *sample)
{
    Sound_SampleInternal *internal = (Sound_SampleInternal *) sample->opaque;
    clean up anything you put into internal->decoder_private;
} /* FMT_close */


static Uint32 FMT_read(Sound_Sample *sample)
{
    Uint32 retval;
    Sound_SampleInternal *internal = (Sound_SampleInternal *) sample->opaque;

        /*
         * We don't actually do any decoding, so we read the fmt data
         *  directly into the internal buffer...
         */
    retval = SDL_RWread(internal->rw, internal->buffer,
                        1, internal->buffer_size);

    (or whatever. Do some decoding here...)

        /* Make sure the read went smoothly... */
    if (retval == 0)
        sample->flags |= SOUND_SAMPLEFLAG_EOF;

    else if (retval == -1)
        sample->flags |= SOUND_SAMPLEFLAG_ERROR;

        /* (next call this EAGAIN may turn into an EOF or error.) */
    else if (retval < internal->buffer_size)
        sample->flags |= SOUND_SAMPLEFLAG_EAGAIN;

    (or whatever. retval == number of bytes you put in internal->buffer).

    return(retval);
} /* FMT_read */


static int FMT_rewind(Sound_Sample *sample)
{
    Sound_SampleInternal *internal = (Sound_SampleInternal *) sample->opaque;

        /* seek to the appropriate place... */
    BAIL_IF_MACRO(SDL_RWseek(internal->rw, 0, SEEK_SET) != 0, ERR_IO_ERROR, 0);

    (reset state as necessary.)

    return(1);  /* success. */
} /* FMT_rewind */


static int FMT_seek(Sound_Sample *sample, Uint32 ms)
{
    Sound_SampleInternal *internal = (Sound_SampleInternal *) sample->opaque;

        /* seek to the appropriate place... */
    BAIL_IF_MACRO(SDL_RWseek(internal->rw, 0, SEEK_SET) != 0, ERR_IO_ERROR, 0);

    (set state as necessary.)

    return(1);  /* success. */
} /* FMT_seek */


#endif /* SOUND_SUPPORTS_FMT */


/* end of fmt.c ... */