Mercurial > SDL_sound_CoreAudio
comparison decoders/shn.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 | b4abd7c48b6e |
children | 3e705c9180e5 |
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473:1edb89260487 | 474:c66080364dff |
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549 Sound_SampleInternal *internal = (Sound_SampleInternal *) sample->opaque; | 549 Sound_SampleInternal *internal = (Sound_SampleInternal *) sample->opaque; |
550 SDL_RWops *rw = internal->rw; | 550 SDL_RWops *rw = internal->rw; |
551 Uint16 u16; | 551 Uint16 u16; |
552 Uint32 u32; | 552 Uint32 u32; |
553 Sint32 cklen; | 553 Sint32 cklen; |
554 Uint32 bytes_per_second; | |
554 | 555 |
555 BAIL_IF_MACRO(!uvar_get(SHN_VERBATIM_CKSIZE_SIZE, shn, rw, &cklen), NULL, 0); | 556 BAIL_IF_MACRO(!uvar_get(SHN_VERBATIM_CKSIZE_SIZE, shn, rw, &cklen), NULL, 0); |
556 | 557 |
557 BAIL_IF_MACRO(!verb_ReadLE32(shn, rw, &u32), NULL, 0); /* RIFF header */ | 558 BAIL_IF_MACRO(!verb_ReadLE32(shn, rw, &u32), NULL, 0); /* RIFF header */ |
558 BAIL_IF_MACRO(u32 != riffID, "SHN: No RIFF header.", 0); | 559 BAIL_IF_MACRO(u32 != riffID, "SHN: No RIFF header.", 0); |
570 sample->actual.channels = u16; | 571 sample->actual.channels = u16; |
571 BAIL_IF_MACRO(!verb_ReadLE32(shn, rw, &u32), NULL, 0); /* sample rate */ | 572 BAIL_IF_MACRO(!verb_ReadLE32(shn, rw, &u32), NULL, 0); /* sample rate */ |
572 sample->actual.rate = u32; | 573 sample->actual.rate = u32; |
573 | 574 |
574 BAIL_IF_MACRO(!verb_ReadLE32(shn, rw, &u32), NULL, 0); /* bytespersec */ | 575 BAIL_IF_MACRO(!verb_ReadLE32(shn, rw, &u32), NULL, 0); /* bytespersec */ |
576 bytes_per_second = u32; | |
575 BAIL_IF_MACRO(!verb_ReadLE16(shn, rw, &u16), NULL, 0); /* blockalign */ | 577 BAIL_IF_MACRO(!verb_ReadLE16(shn, rw, &u16), NULL, 0); /* blockalign */ |
576 BAIL_IF_MACRO(!verb_ReadLE16(shn, rw, &u16), NULL, 0); /* bitspersample */ | 578 BAIL_IF_MACRO(!verb_ReadLE16(shn, rw, &u16), NULL, 0); /* bitspersample */ |
577 | 579 |
578 BAIL_IF_MACRO(!verb_ReadLE32(shn, rw, &u32), NULL, 0); /* 'data' header */ | 580 BAIL_IF_MACRO(!verb_ReadLE32(shn, rw, &u32), NULL, 0); /* 'data' header */ |
579 BAIL_IF_MACRO(u32 != dataID, "SHN: No 'data' header.", 0); | 581 BAIL_IF_MACRO(u32 != dataID, "SHN: No 'data' header.", 0); |
580 BAIL_IF_MACRO(!verb_ReadLE32(shn, rw, &u32), NULL, 0); /* chunksize */ | 582 BAIL_IF_MACRO(!verb_ReadLE32(shn, rw, &u32), NULL, 0); /* chunksize */ |
581 | 583 sample->total_time = u32 / bytes_per_second * 1000; |
584 sample->total_time += (u32 % bytes_per_second) * 1000 / bytes_per_second; | |
582 return(1); | 585 return(1); |
583 } /* parse_riff_header */ | 586 } /* parse_riff_header */ |
584 | 587 |
585 | 588 |
586 static int SHN_open(Sound_Sample *sample, const char *ext) | 589 static int SHN_open(Sound_Sample *sample, const char *ext) |