ref: 25982e4ff28ba2d92131db29adcd2b940b2f6bad
parent: c7709bad17ca756694a68aed2696f993ed9056ce
author: cbagwell <cbagwell>
date: Sun Jan 9 11:20:55 EST 2011
add seek support which must read samples but can skip unneeded decoding and should be faster. Patch from Pavel Karneliuk.
--- a/ChangeLog
+++ b/ChangeLog
@@ -13,6 +13,7 @@
o Fix regression where MP3 handler required libmad headers to be installed.
(Samuli Suominen)
+ o Add seek support to mp3 handler for speed improvements. (Pavel Karneliuk)
Audio device drivers:
--- a/src/mp3.c
+++ b/src/mp3.c
@@ -524,6 +524,110 @@
LSX_DLLIBRARY_CLOSE(p, mad_dl);
return SOX_SUCCESS;
}
+
+static int sox_mp3seek(sox_format_t * ft, uint64_t offset)
+{+ priv_t * p = (priv_t *) ft->priv;
+ size_t initial_bitrate = p->Frame.header.bitrate;
+ size_t tagsize = 0, consumed = 0;
+ sox_bool vbr = sox_false; /* Variable Bit Rate */
+ sox_bool depadded = sox_false;
+ uint64_t to_skip_samples = 0;
+
+ /* Reset all */
+ rewind(ft->fp);
+ mad_timer_reset(&p->Timer);
+ p->FrameCount = 0;
+
+ /* They where opened in startread */
+ mad_synth_finish(&p->Synth);
+ p->mad_frame_finish(&p->Frame);
+ p->mad_stream_finish(&p->Stream);
+
+ p->mad_stream_init(&p->Stream);
+ p->mad_frame_init(&p->Frame);
+ p->mad_synth_init(&p->Synth);
+
+ offset /= ft->signal.channels;
+ to_skip_samples = offset;
+
+ while(sox_true) { /* Read data from the MP3 file */+ int read, padding = 0;
+ size_t leftover = p->Stream.bufend - p->Stream.next_frame;
+
+ memcpy(p->mp3_buffer, p->Stream.this_frame, leftover);
+ read = fread(p->mp3_buffer + leftover, (size_t) 1, p->mp3_buffer_size - leftover, ft->fp);
+ if (read <= 0) {+ lsx_debug("seek failure. unexpected EOF (frames=%lu leftover=%lu)", (unsigned long)p->FrameCount, (unsigned long)leftover);+ break;
+ }
+ for (; !depadded && padding < read && !p->mp3_buffer[padding]; ++padding);
+ depadded = sox_true;
+ p->mad_stream_buffer(&p->Stream, p->mp3_buffer + padding, leftover + read - padding);
+
+ while (to_skip_samples > 0) { /* Decode frame headers */+ static unsigned short samples;
+ p->Stream.error = MAD_ERROR_NONE;
+
+ /* Not an audio frame */
+ if (p->mad_header_decode(&p->Frame.header, &p->Stream) == -1) {+ if (p->Stream.error == MAD_ERROR_BUFLEN)
+ break; /* Normal behaviour; get some more data from the file */
+ if (!MAD_RECOVERABLE(p->Stream.error)) {+ lsx_warn("unrecoverable MAD error");+ break;
+ }
+ if (p->Stream.error == MAD_ERROR_LOSTSYNC) {+ unsigned available = (p->Stream.bufend - p->Stream.this_frame);
+ tagsize = tagtype(p->Stream.this_frame, (size_t) available);
+ if (tagsize) { /* It's some ID3 tags, so just skip */+ if (tagsize >= available) {+ fseeko(ft->fp, (off_t)(tagsize - available), SEEK_CUR);
+ depadded = sox_false;
+ }
+ p->mad_stream_skip(&p->Stream, min(tagsize, available));
+ }
+ else lsx_warn("MAD lost sync");+ }
+ else lsx_warn("recoverable MAD error");+ continue;
+ }
+
+ consumed += p->Stream.next_frame - p->Stream.this_frame;
+ vbr |= (p->Frame.header.bitrate != initial_bitrate);
+
+ samples = 32 * MAD_NSBSAMPLES(&p->Frame.header);
+
+ p->FrameCount++;
+ p->mad_timer_add(&p->Timer, p->Frame.header.duration);
+
+ if(to_skip_samples <= samples)
+ {+ p->mad_frame_decode(&p->Frame,&p->Stream);
+ p->mad_synth_frame(&p->Synth, &p->Frame);
+ p->cursamp = to_skip_samples;
+ return SOX_SUCCESS;
+ }
+ else to_skip_samples -= samples;
+
+ /* If not VBR, we can extrapolate frame size */
+ if (p->FrameCount == 64 && !vbr) {+ p->FrameCount = offset / samples;
+ to_skip_samples = offset % samples;
+
+ if (SOX_SUCCESS != lsx_seeki(ft, (p->FrameCount * consumed / 64) + tagsize, SEEK_SET))
+ return SOX_EOF;
+
+ /* Reset Stream for refilling buffer */
+ p->mad_stream_finish(&p->Stream);
+ p->mad_stream_init(&p->Stream);
+ break;
+ }
+ }
+ };
+
+ return SOX_EOF;
+}
#else /*HAVE_MAD_H*/
static int startread(sox_format_t * ft)
{@@ -532,6 +636,7 @@
}
#define sox_mp3read NULL
#define stopread NULL
+#define sox_mp3seek NULL
#endif /*HAVE_MAD_H*/
#ifdef HAVE_LAME
@@ -1014,7 +1119,7 @@
"MPEG Layer 3 lossy audio compression", names, 0,
startread, sox_mp3read, stopread,
startwrite, sox_mp3write, stopwrite,
- NULL, write_encodings, NULL, sizeof(priv_t)
+ sox_mp3seek, write_encodings, NULL, sizeof(priv_t)
};
return &handler;
}