Mercurial > SDL_sound_CoreAudio
annotate decoders/mpglib/layer1.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 | ad4c8f34136a |
| children |
| rev | line source |
|---|---|
| 261 | 1 /* |
| 2 * Mpeg Layer-1 audio decoder | |
| 3 * -------------------------- | |
| 4 * copyright (c) 1995 by Michael Hipp, All rights reserved. See also 'README' | |
| 5 * near unoptimzed ... | |
| 6 * | |
| 7 * may have a few bugs after last optimization ... | |
| 8 * | |
| 9 */ | |
| 10 | |
| 11 #include "mpg123_sdlsound.h" | |
| 12 | |
| 13 void I_step_one(unsigned int balloc[], unsigned int scale_index[2][SBLIMIT],struct frame *fr) | |
| 14 { | |
| 15 unsigned int *ba=balloc; | |
| 16 unsigned int *sca = (unsigned int *) scale_index; | |
| 17 | |
| 18 if(fr->stereo) { | |
| 19 int i; | |
| 20 int jsbound = fr->jsbound; | |
| 21 for (i=0;i<jsbound;i++) { | |
| 22 *ba++ = getbits(4); | |
| 23 *ba++ = getbits(4); | |
| 24 } | |
| 25 for (i=jsbound;i<SBLIMIT;i++) | |
| 26 *ba++ = getbits(4); | |
| 27 | |
| 28 ba = balloc; | |
| 29 | |
| 30 for (i=0;i<jsbound;i++) { | |
| 31 if ((*ba++)) | |
| 32 *sca++ = getbits(6); | |
| 33 if ((*ba++)) | |
| 34 *sca++ = getbits(6); | |
| 35 } | |
| 36 for (i=jsbound;i<SBLIMIT;i++) | |
| 37 if ((*ba++)) { | |
| 38 *sca++ = getbits(6); | |
| 39 *sca++ = getbits(6); | |
| 40 } | |
| 41 } | |
| 42 else { | |
| 43 int i; | |
| 44 for (i=0;i<SBLIMIT;i++) | |
| 45 *ba++ = getbits(4); | |
| 46 ba = balloc; | |
| 47 for (i=0;i<SBLIMIT;i++) | |
| 48 if ((*ba++)) | |
| 49 *sca++ = getbits(6); | |
| 50 } | |
| 51 } | |
| 52 | |
| 53 void I_step_two(real fraction[2][SBLIMIT],unsigned int balloc[2*SBLIMIT], | |
| 54 unsigned int scale_index[2][SBLIMIT],struct frame *fr) | |
| 55 { | |
| 56 int i,n; | |
| 57 int smpb[2*SBLIMIT]; /* values: 0-65535 */ | |
| 58 int *sample; | |
| 59 register unsigned int *ba; | |
| 60 register unsigned int *sca = (unsigned int *) scale_index; | |
| 61 | |
| 62 if(fr->stereo) { | |
| 63 int jsbound = fr->jsbound; | |
| 64 register real *f0 = fraction[0]; | |
| 65 register real *f1 = fraction[1]; | |
| 66 ba = balloc; | |
| 67 for (sample=smpb,i=0;i<jsbound;i++) { | |
| 68 if ((n = *ba++)) | |
| 69 *sample++ = getbits(n+1); | |
| 70 if ((n = *ba++)) | |
| 71 *sample++ = getbits(n+1); | |
| 72 } | |
| 73 for (i=jsbound;i<SBLIMIT;i++) | |
| 74 if ((n = *ba++)) | |
| 75 *sample++ = getbits(n+1); | |
| 76 | |
| 77 ba = balloc; | |
| 78 for (sample=smpb,i=0;i<jsbound;i++) { | |
| 79 if((n=*ba++)) | |
| 80 *f0++ = (real) ( ((-1)<<n) + (*sample++) + 1) * muls[n+1][*sca++]; | |
| 81 else | |
| 82 *f0++ = 0.0; | |
| 83 if((n=*ba++)) | |
| 84 *f1++ = (real) ( ((-1)<<n) + (*sample++) + 1) * muls[n+1][*sca++]; | |
| 85 else | |
| 86 *f1++ = 0.0; | |
| 87 } | |
| 88 for (i=jsbound;i<SBLIMIT;i++) { | |
| 89 if ((n=*ba++)) { | |
| 90 real samp = ( ((-1)<<n) + (*sample++) + 1); | |
| 91 *f0++ = samp * muls[n+1][*sca++]; | |
| 92 *f1++ = samp * muls[n+1][*sca++]; | |
| 93 } | |
| 94 else | |
| 95 *f0++ = *f1++ = 0.0; | |
| 96 } | |
| 97 } | |
| 98 else { | |
| 99 register real *f0 = fraction[0]; | |
| 100 ba = balloc; | |
| 101 for (sample=smpb,i=0;i<SBLIMIT;i++) | |
| 102 if ((n = *ba++)) | |
| 103 *sample++ = getbits(n+1); | |
| 104 ba = balloc; | |
| 105 for (sample=smpb,i=0;i<SBLIMIT;i++) { | |
| 106 if((n=*ba++)) | |
| 107 *f0++ = (real) ( ((-1)<<n) + (*sample++) + 1) * muls[n+1][*sca++]; | |
| 108 else | |
| 109 *f0++ = 0.0; | |
| 110 } | |
| 111 } | |
| 112 } | |
| 113 | |
|
281
ad4c8f34136a
Minor formatting updates.
Ryan C. Gordon <icculus@icculus.org>
parents:
279
diff
changeset
|
114 int do_layer1(struct frame *fr,unsigned char *pcm_sample, |
|
ad4c8f34136a
Minor formatting updates.
Ryan C. Gordon <icculus@icculus.org>
parents:
279
diff
changeset
|
115 int *pcm_point,struct mpstr *mp) |
| 261 | 116 { |
| 117 int clip=0; | |
| 118 int i,stereo = fr->stereo; | |
| 119 unsigned int balloc[2*SBLIMIT]; | |
| 120 unsigned int scale_index[2][SBLIMIT]; | |
| 121 real fraction[2][SBLIMIT]; | |
| 122 int single = fr->single; | |
| 123 | |
| 124 fr->jsbound = (fr->mode == MPG_MD_JOINT_STEREO) ? (fr->mode_ext<<2)+4 : 32; | |
| 125 | |
| 126 if(stereo == 1 || single == 3) | |
| 127 single = 0; | |
| 128 | |
| 129 I_step_one(balloc,scale_index,fr); | |
| 130 | |
| 131 for (i=0;i<SCALE_BLOCK;i++) | |
| 132 { | |
| 133 I_step_two(fraction,balloc,scale_index,fr); | |
| 134 | |
| 135 if(single >= 0) { | |
|
279
52b9f37998db
Removed global state variable; should be thread safe now.
Ryan C. Gordon <icculus@icculus.org>
parents:
261
diff
changeset
|
136 clip += synth_1to1_mono( (real*)fraction[single],pcm_sample,pcm_point,mp); |
| 261 | 137 } |
| 138 else { | |
| 139 int p1 = *pcm_point; | |
|
279
52b9f37998db
Removed global state variable; should be thread safe now.
Ryan C. Gordon <icculus@icculus.org>
parents:
261
diff
changeset
|
140 clip += synth_1to1( (real*)fraction[0],0,pcm_sample,&p1,mp); |
|
52b9f37998db
Removed global state variable; should be thread safe now.
Ryan C. Gordon <icculus@icculus.org>
parents:
261
diff
changeset
|
141 clip += synth_1to1( (real*)fraction[1],1,pcm_sample,pcm_point,mp); |
| 261 | 142 } |
| 143 } | |
| 144 | |
| 145 return clip; | |
| 146 } | |
| 147 | |
| 148 |