Diff: frame.cpp

Revision:

0:7627c79db971

Child:

2:f28cf0afd021

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/frame.cpp	Fri Nov 26 12:18:30 2010 +0000
@@ -0,0 +1,501 @@
+/*
+ * libmad - MPEG audio decoder library
+ * Copyright (C) 2000-2004 Underbit Technologies, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ * $Id: frame.c,v 1.1 2010/11/23 20:12:57 andy Exp $
+ */
+
+#  include "config.h"
+
+# include "global.h"
+
+# include <stdlib.h>
+
+# include "bit.h"
+# include "stream.h"
+# include "frame.h"
+# include "timer.h"
+# include "layer12.h"
+# include "layer3.h"
+
+static
+unsigned long const bitrate_table[5][15] = {
+  /* MPEG-1 */
+  { 0,  32000,  64000,  96000, 128000, 160000, 192000, 224000,  /* Layer I   */
+       256000, 288000, 320000, 352000, 384000, 416000, 448000 },
+  { 0,  32000,  48000,  56000,  64000,  80000,  96000, 112000,  /* Layer II  */
+       128000, 160000, 192000, 224000, 256000, 320000, 384000 },
+  { 0,  32000,  40000,  48000,  56000,  64000,  80000,  96000,  /* Layer III */
+       112000, 128000, 160000, 192000, 224000, 256000, 320000 },
+
+  /* MPEG-2 LSF */
+  { 0,  32000,  48000,  56000,  64000,  80000,  96000, 112000,  /* Layer I   */
+       128000, 144000, 160000, 176000, 192000, 224000, 256000 },
+  { 0,   8000,  16000,  24000,  32000,  40000,  48000,  56000,  /* Layers    */
+        64000,  80000,  96000, 112000, 128000, 144000, 160000 } /* II & III  */
+};
+
+static
+unsigned int const samplerate_table[3] = { 44100, 48000, 32000 };
+
+static
+int (*const decoder_table[3])(struct mad_stream *, struct mad_frame *) = {
+  mad_layer_I,
+  mad_layer_II,
+  mad_layer_III
+};
+
+/*
+ * NAME:	header->init()
+ * DESCRIPTION:	initialize header struct
+ */
+void mad_header_init(struct mad_header *header)
+{
+  header->layer          = (enum mad_layer)0;
+  header->mode           = (enum mad_mode)0;
+  header->mode_extension = 0;
+  header->emphasis       = (enum mad_emphasis)0;
+
+  header->bitrate        = 0;
+  header->samplerate     = 0;
+
+  header->crc_check      = 0;
+  header->crc_target     = 0;
+
+  header->flags          = 0;
+  header->private_bits   = 0;
+
+  header->duration       = mad_timer_zero;
+}
+
+/*
+ * NAME:	frame->init()
+ * DESCRIPTION:	initialize frame struct
+ */
+void mad_frame_init(struct mad_frame *frame)
+{
+  mad_header_init(&frame->header);
+
+  frame->options = 0;
+
+  frame->overlap = 0;
+  mad_frame_mute(frame);
+}
+
+/*
+ * NAME:	frame->finish()
+ * DESCRIPTION:	deallocate any dynamic memory associated with frame
+ */
+void mad_frame_finish(struct mad_frame *frame)
+{
+  mad_header_finish(&frame->header);
+
+  if (frame->overlap) {
+    free(frame->overlap);
+    frame->overlap = 0;
+  }
+}
+
+/*
+ * NAME:	decode_header()
+ * DESCRIPTION:	read header data and following CRC word
+ */
+static
+int decode_header(struct mad_header *header, struct mad_stream *stream)
+{
+  unsigned int index;
+
+  header->flags        = 0;
+  header->private_bits = 0;
+
+  /* header() */
+
+  /* syncword */
+  mad_bit_skip(&stream->ptr, 11);
+
+  /* MPEG 2.5 indicator (really part of syncword) */
+  if (mad_bit_read(&stream->ptr, 1) == 0)
+    header->flags |= MAD_FLAG_MPEG_2_5_EXT;
+
+  /* ID */
+  if (mad_bit_read(&stream->ptr, 1) == 0)
+    header->flags |= MAD_FLAG_LSF_EXT;
+  else if (header->flags & MAD_FLAG_MPEG_2_5_EXT) {
+    stream->error = MAD_ERROR_LOSTSYNC;
+    return -1;
+  }
+
+  /* layer */
+  header->layer = (enum mad_layer)(4 - mad_bit_read(&stream->ptr, 2));
+
+  if (header->layer == 4) {
+    stream->error = MAD_ERROR_BADLAYER;
+    return -1;
+  }
+
+  /* protection_bit */
+  if (mad_bit_read(&stream->ptr, 1) == 0) {
+    header->flags    |= MAD_FLAG_PROTECTION;
+    header->crc_check = mad_bit_crc(stream->ptr, 16, 0xffff);
+  }
+
+  /* bitrate_index */
+  index = mad_bit_read(&stream->ptr, 4);
+
+  if (index == 15) {
+    stream->error = MAD_ERROR_BADBITRATE;
+    return -1;
+  }
+
+  if (header->flags & MAD_FLAG_LSF_EXT)
+    header->bitrate = bitrate_table[3 + (header->layer >> 1)][index];
+  else
+    header->bitrate = bitrate_table[header->layer - 1][index];
+
+  /* sampling_frequency */
+  index = mad_bit_read(&stream->ptr, 2);
+
+  if (index == 3) {
+    stream->error = MAD_ERROR_BADSAMPLERATE;
+    return -1;
+  }
+
+  header->samplerate = samplerate_table[index];
+
+  if (header->flags & MAD_FLAG_LSF_EXT) {
+    header->samplerate /= 2;
+
+    if (header->flags & MAD_FLAG_MPEG_2_5_EXT)
+      header->samplerate /= 2;
+  }
+
+  /* padding_bit */
+  if (mad_bit_read(&stream->ptr, 1))
+    header->flags |= MAD_FLAG_PADDING;
+
+  /* private_bit */
+  if (mad_bit_read(&stream->ptr, 1))
+    header->private_bits |= MAD_PRIVATE_HEADER;
+
+  /* mode */
+  header->mode = (enum mad_mode)(3 - mad_bit_read(&stream->ptr, 2));
+
+  /* mode_extension */
+  header->mode_extension = mad_bit_read(&stream->ptr, 2);
+
+  /* copyright */
+  if (mad_bit_read(&stream->ptr, 1))
+    header->flags |= MAD_FLAG_COPYRIGHT;
+
+  /* original/copy */
+  if (mad_bit_read(&stream->ptr, 1))
+    header->flags |= MAD_FLAG_ORIGINAL;
+
+  /* emphasis */
+  header->emphasis = (enum mad_emphasis)mad_bit_read(&stream->ptr, 2);
+
+# if defined(OPT_STRICT)
+  /*
+   * ISO/IEC 11172-3 says this is a reserved emphasis value, but
+   * streams exist which use it anyway. Since the value is not important
+   * to the decoder proper, we allow it unless OPT_STRICT is defined.
+   */
+  if (header->emphasis == MAD_EMPHASIS_RESERVED) {
+    stream->error = MAD_ERROR_BADEMPHASIS;
+    return -1;
+  }
+# endif
+
+  /* error_check() */
+
+  /* crc_check */
+  if (header->flags & MAD_FLAG_PROTECTION)
+    header->crc_target = mad_bit_read(&stream->ptr, 16);
+
+  return 0;
+}
+
+/*
+ * NAME:	free_bitrate()
+ * DESCRIPTION:	attempt to discover the bitstream's free bitrate
+ */
+static
+int free_bitrate(struct mad_stream *stream, struct mad_header const *header)
+{
+  struct mad_bitptr keep_ptr;
+  unsigned long rate = 0;
+  unsigned int pad_slot, slots_per_frame;
+  unsigned char const *ptr = 0;
+
+  keep_ptr = stream->ptr;
+
+  pad_slot = (header->flags & MAD_FLAG_PADDING) ? 1 : 0;
+  slots_per_frame = (header->layer == MAD_LAYER_III &&
+		     (header->flags & MAD_FLAG_LSF_EXT)) ? 72 : 144;
+
+  while (mad_stream_sync(stream) == 0) {
+    struct mad_stream peek_stream;
+    struct mad_header peek_header;
+
+    peek_stream = *stream;
+    peek_header = *header;
+
+    if (decode_header(&peek_header, &peek_stream) == 0 &&
+	peek_header.layer == header->layer &&
+	peek_header.samplerate == header->samplerate) {
+      unsigned int N;
+
+      ptr = mad_bit_nextbyte(&stream->ptr);
+
+      N = ptr - stream->this_frame;
+
+      if (header->layer == MAD_LAYER_I) {
+	rate = (unsigned long) header->samplerate *
+	  (N - 4 * pad_slot + 4) / 48 / 1000;
+      }
+      else {
+	rate = (unsigned long) header->samplerate *
+	  (N - pad_slot + 1) / slots_per_frame / 1000;
+      }
+
+      if (rate >= 8)
+	break;
+    }
+
+    mad_bit_skip(&stream->ptr, 8);
+  }
+
+  stream->ptr = keep_ptr;
+
+  if (rate < 8 || (header->layer == MAD_LAYER_III && rate > 640)) {
+    stream->error = MAD_ERROR_LOSTSYNC;
+    return -1;
+  }
+
+  stream->freerate = rate * 1000;
+
+  return 0;
+}
+
+/*
+ * NAME:	header->decode()
+ * DESCRIPTION:	read the next frame header from the stream
+ */
+int mad_header_decode(struct mad_header *header, struct mad_stream *stream)
+{
+  register unsigned char const *ptr, *end;
+  unsigned int pad_slot, N;
+
+  ptr = stream->next_frame;
+  end = stream->bufend;
+
+  if (ptr == 0) {
+    stream->error = MAD_ERROR_BUFPTR;
+    goto fail;
+  }
+
+  /* stream skip */
+  if (stream->skiplen) {
+    if (!stream->sync)
+      ptr = stream->this_frame;
+
+    if (end - ptr < stream->skiplen) {
+      stream->skiplen   -= end - ptr;
+      stream->next_frame = end;
+
+      stream->error = MAD_ERROR_BUFLEN;
+      goto fail;
+    }
+
+    ptr += stream->skiplen;
+    stream->skiplen = 0;
+
+    stream->sync = 1;
+  }
+
+ sync:
+  /* synchronize */
+  if (stream->sync) {
+    if (end - ptr < MAD_BUFFER_GUARD) {
+      stream->next_frame = ptr;
+
+      stream->error = MAD_ERROR_BUFLEN;
+      goto fail;
+    }
+    else if (!(ptr[0] == 0xff && (ptr[1] & 0xe0) == 0xe0)) {
+      /* mark point where frame sync word was expected */
+      stream->this_frame = ptr;
+      stream->next_frame = ptr + 1;
+
+      stream->error = MAD_ERROR_LOSTSYNC;
+      goto fail;
+    }
+  }
+  else {
+    mad_bit_init(&stream->ptr, ptr);
+
+    if (mad_stream_sync(stream) == -1) {
+      if (end - stream->next_frame >= MAD_BUFFER_GUARD)
+	stream->next_frame = end - MAD_BUFFER_GUARD;
+
+      stream->error = MAD_ERROR_BUFLEN;
+      goto fail;
+    }
+
+    ptr = mad_bit_nextbyte(&stream->ptr);
+  }
+
+  /* begin processing */
+  stream->this_frame = ptr;
+  stream->next_frame = ptr + 1;  /* possibly bogus sync word */
+
+  mad_bit_init(&stream->ptr, stream->this_frame);
+
+  if (decode_header(header, stream) == -1)
+    goto fail;
+
+  /* calculate frame duration */
+  mad_timer_set(&header->duration, 0,
+		32 * MAD_NSBSAMPLES(header), header->samplerate);
+
+  /* calculate free bit rate */
+  if (header->bitrate == 0) {
+    if ((stream->freerate == 0 || !stream->sync ||
+	 (header->layer == MAD_LAYER_III && stream->freerate > 640000)) &&
+	free_bitrate(stream, header) == -1)
+      goto fail;
+
+    header->bitrate = stream->freerate;
+    header->flags  |= MAD_FLAG_FREEFORMAT;
+  }
+
+  /* calculate beginning of next frame */
+  pad_slot = (header->flags & MAD_FLAG_PADDING) ? 1 : 0;
+
+  if (header->layer == MAD_LAYER_I)
+    N = ((12 * header->bitrate / header->samplerate) + pad_slot) * 4;
+  else {
+    unsigned int slots_per_frame;
+
+    slots_per_frame = (header->layer == MAD_LAYER_III &&
+		       (header->flags & MAD_FLAG_LSF_EXT)) ? 72 : 144;
+
+    N = (slots_per_frame * header->bitrate / header->samplerate) + pad_slot;
+  }
+
+  /* verify there is enough data left in buffer to decode this frame */
+  if (N + MAD_BUFFER_GUARD > end - stream->this_frame) {
+    stream->next_frame = stream->this_frame;
+
+    stream->error = MAD_ERROR_BUFLEN;
+    goto fail;
+  }
+
+  stream->next_frame = stream->this_frame + N;
+
+  if (!stream->sync) {
+    /* check that a valid frame header follows this frame */
+
+    ptr = stream->next_frame;
+    if (!(ptr[0] == 0xff && (ptr[1] & 0xe0) == 0xe0)) {
+      ptr = stream->next_frame = stream->this_frame + 1;
+      goto sync;
+    }
+
+    stream->sync = 1;
+  }
+
+  header->flags |= MAD_FLAG_INCOMPLETE;
+
+  return 0;
+
+ fail:
+  stream->sync = 0;
+
+  return -1;
+}
+
+/*
+ * NAME:	frame->decode()
+ * DESCRIPTION:	decode a single frame from a bitstream
+ */
+int mad_frame_decode(struct mad_frame *frame, struct mad_stream *stream)
+{
+  frame->options = stream->options;
+
+  /* header() */
+  /* error_check() */
+
+  if (!(frame->header.flags & MAD_FLAG_INCOMPLETE) &&
+      mad_header_decode(&frame->header, stream) == -1)
+    goto fail;
+
+  /* audio_data() */
+
+  frame->header.flags &= ~MAD_FLAG_INCOMPLETE;
+
+  if (decoder_table[frame->header.layer - 1](stream, frame) == -1) {
+    if (!MAD_RECOVERABLE(stream->error))
+      stream->next_frame = stream->this_frame;
+
+    goto fail;
+  }
+
+  /* ancillary_data() */
+
+  if (frame->header.layer != MAD_LAYER_III) {
+    struct mad_bitptr next_frame;
+
+    mad_bit_init(&next_frame, stream->next_frame);
+
+    stream->anc_ptr    = stream->ptr;
+    stream->anc_bitlen = mad_bit_length(&stream->ptr, &next_frame);
+
+    mad_bit_finish(&next_frame);
+  }
+
+  return 0;
+
+ fail:
+  stream->anc_bitlen = 0;
+  return -1;
+}
+
+/*
+ * NAME:	frame->mute()
+ * DESCRIPTION:	zero all subband values so the frame becomes silent
+ */
+void mad_frame_mute(struct mad_frame *frame)
+{
+  unsigned int s, sb;
+
+  for (s = 0; s < 36; ++s) {
+    for (sb = 0; sb < 32; ++sb) {
+      frame->sbsample[0][s][sb] =
+      frame->sbsample[1][s][sb] = 0;
+    }
+  }
+
+  if (frame->overlap) {
+    for (s = 0; s < 18; ++s) {
+      for (sb = 0; sb < 32; ++sb) {
+	(*frame->overlap)[0][sb][s] =
+	(*frame->overlap)[1][sb][s] = 0;
+      }
+    }
+  }
+}