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120 lines
4.2 KiB
C
120 lines
4.2 KiB
C
/*
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sampleadjust: gapless sample offset math
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copyright 1995-2012 by the mpg123 project - free software under the terms of the LGPL 2.1
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see COPYING and AUTHORS files in distribution or http://mpg123.org
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This is no stand-alone header, precisely to be able to fool it into using fake handle types for testing the math.
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*/
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#include "debug.h"
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#ifdef GAPLESS
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/* From internal sample number to external. */
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static off_t sample_adjust(mpg123_handle *mh, off_t x)
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{
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off_t s;
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if(mh->p.flags & MPG123_GAPLESS)
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{
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/* It's a bit tricky to do this computation for the padding samples.
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They are not there on the outside. */
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if(x > mh->end_os)
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{
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if(x < mh->fullend_os)
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s = mh->end_os - mh->begin_os;
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else
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s = x - (mh->fullend_os - mh->end_os + mh->begin_os);
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}
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else
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s = x - mh->begin_os;
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}
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else
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s = x;
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return s;
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}
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/* from external samples to internal */
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static off_t sample_unadjust(mpg123_handle *mh, off_t x)
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{
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off_t s;
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if(mh->p.flags & MPG123_GAPLESS)
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{
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s = x + mh->begin_os;
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/* There is a hole; we don't create sample positions in there.
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Jump from the end of the gapless track directly to after the padding. */
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if(s >= mh->end_os)
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s += mh->fullend_os - mh->end_os;
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}
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else s = x;
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return s;
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}
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/*
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Take the buffer after a frame decode (strictly: it is the data from frame fr->num!) and cut samples out.
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fr->buffer.fill may then be smaller than before...
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*/
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static void frame_buffercheck(mpg123_handle *fr)
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{
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/* When we have no accurate position, gapless code does not make sense. */
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if(!(fr->state_flags & FRAME_ACCURATE)) return;
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/* Get a grip on dirty streams that start with a gapless header.
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Simply accept all data from frames that are too much,
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they are supposedly attached to the stream after the fact. */
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if(fr->gapless_frames > 0 && fr->num >= fr->gapless_frames) return;
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/* Important: We first cut samples from the end, then cut from beginning (including left-shift of the buffer).
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This order works also for the case where firstframe == lastframe. */
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/* The last interesting (planned) frame: Only use some leading samples.
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Note a difference from the below: The last frame and offset are unchanges by seeks.
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The lastoff keeps being valid. */
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if(fr->lastframe > -1 && fr->num >= fr->lastframe)
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{
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/* There can be more than one frame of padding at the end, so we ignore the whole frame if we are beyond lastframe. */
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off_t byteoff = (fr->num == fr->lastframe) ? samples_to_bytes(fr, fr->lastoff) : 0;
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if((off_t)fr->buffer.fill > byteoff)
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{
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fr->buffer.fill = byteoff;
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}
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if(VERBOSE3) fprintf(stderr, "\nNote: Cut frame %"OFF_P" buffer on end of stream to %"OFF_P" samples, fill now %"SIZE_P" bytes.\n", (off_p)fr->num, (off_p)(fr->num == fr->lastframe ? fr->lastoff : 0), (size_p)fr->buffer.fill);
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}
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/* The first interesting frame: Skip some leading samples. */
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if(fr->firstoff && fr->num == fr->firstframe)
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{
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off_t byteoff = samples_to_bytes(fr, fr->firstoff);
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if((off_t)fr->buffer.fill > byteoff)
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{
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fr->buffer.fill -= byteoff;
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/* buffer.p != buffer.data only for own buffer */
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debug6("cutting %li samples/%li bytes on begin, own_buffer=%i at %p=%p, buf[1]=%i",
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(long)fr->firstoff, (long)byteoff, fr->own_buffer, (void*)fr->buffer.p, (void*)fr->buffer.data, ((short*)fr->buffer.p)[2]);
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if(fr->own_buffer) fr->buffer.p = fr->buffer.data + byteoff;
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else memmove(fr->buffer.data, fr->buffer.data + byteoff, fr->buffer.fill);
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debug3("done cutting, buffer at %p =? %p, buf[1]=%i",
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(void*)fr->buffer.p, (void*)fr->buffer.data, ((short*)fr->buffer.p)[2]);
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}
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else fr->buffer.fill = 0;
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if(VERBOSE3) fprintf(stderr, "\nNote: Cut frame %"OFF_P" buffer on beginning of stream by %"OFF_P" samples, fill now %"SIZE_P" bytes.\n", (off_p)fr->num, (off_p)fr->firstoff, (size_p)fr->buffer.fill);
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/* We can only reach this frame again by seeking. And on seeking, firstoff will be recomputed.
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So it is safe to null it here (and it makes the if() decision abort earlier). */
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fr->firstoff = 0;
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}
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}
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#define SAMPLE_ADJUST(mh,x) sample_adjust(mh,x)
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#define SAMPLE_UNADJUST(mh,x) sample_unadjust(mh,x)
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#define FRAME_BUFFERCHECK(mh) frame_buffercheck(mh)
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#else /* no gapless code included */
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#define SAMPLE_ADJUST(mh,x) (x)
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#define SAMPLE_UNADJUST(mh,x) (x)
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#define FRAME_BUFFERCHECK(mh)
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#endif
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