view extra_rwops.h @ 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 47cc2de2ae36
children 137c0b00ea4c 50bb9a6cebfe
line wrap: on
line source

/*
 * 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
 */

/*
 * Some extra RWops that are needed or are just handy to have.
 *
 * Please see the file COPYING in the source's root directory.
 *
 *  This file written by Ryan C. Gordon. (icculus@clutteredmind.org)
 */

#ifndef _INCLUDE_EXTRA_RWOPS_H_
#define _INCLUDE_EXTRA_RWOPS_H_

#include "SDL.h"

#ifdef __cplusplus
extern "C" {
#endif

/*
 * The Reference Counter RWops...
 *
 *  This wraps another RWops with a reference counter. When you create a
 *   reference counter RWops, it sets a counter to one. Everytime you call
 *   RWops_RWRefCounter_new(), that's RWops's counter increments by one.
 *   Everytime you call that RWops's close() method, the counter decrements
 *   by one. If the counter hits zero, the original RWops's close() method
 *   is called, and the reference counting wrapper deletes itself. The read,
 *   write, and seek methods just pass through to the original.
 *
 *  This is handy if you have two libraries (in the original case, SDL_sound
 *   and SMPEG), who both want an SDL_RWops, and both want to close it when
 *   they are finished. This resolves that contention. The user creates a
 *   RWops, passes it to SDL_sound, which wraps it in a reference counter and
 *   increments the number of references, and passes the wrapped RWops to
 *   SMPEG. SMPEG "closes" this wrapped RWops when the MP3 has finished
 *   playing, and SDL_sound then closes it, too. This second closing removes
 *   the last reference, and the RWops is smoothly destructed.
 */

/* Return a SDL_RWops that is a reference counting wrapper of (rw). */
SDL_RWops *RWops_RWRefCounter_new(SDL_RWops *rw);

/* Increment a reference counting RWops's refcount by one. */
void RWops_RWRefCounter_addRef(SDL_RWops *rw);

#ifdef __cplusplus
}
#endif

#endif /* !defined _INCLUDE_EXTRA_RWOPS_H_ */

/* end of extra_rwops.h ... */