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comparison decoders/shn.c @ 474:c66080364dff

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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
comparison
equal deleted inserted replaced
473:1edb89260487 474:c66080364dff
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)