Initial revision

Originally committed as revision 5 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 293 insertions, 0 deletions

diff --git a/libavcodec/mpegaudiodec.c b/libavcodec/mpegaudiodec.c
new file mode 100644
index 0000000000..f3fa90af55
--- /dev/null
+++ b/libavcodec/mpegaudiodec.c
@@ -0,0 +1,293 @@
+/*
+ * MPEG Audio decoder
+ * Copyright (c) 2001 Gerard Lantau.
+ *
+ * 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., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include "avcodec.h"
+#include "mpglib/mpg123.h"
+
+/*
+ * TODO: 
+ *  - add free format
+ *  - do not rely anymore on mpglib (first step: implement dct64 and decoding filter)
+ */
+
+#define HEADER_SIZE 4
+#define BACKSTEP_SIZE 512
+
+typedef struct MPADecodeContext {
+    struct mpstr mpstr;
+    UINT8 inbuf1[2][MAXFRAMESIZE + BACKSTEP_SIZE];	/* input buffer */
+    int inbuf_index;
+    UINT8 *inbuf_ptr, *inbuf;
+    int frame_size;
+    int error_protection;
+    int layer;
+    int sample_rate;
+    int bit_rate;
+    int old_frame_size;
+    GetBitContext gb;
+} MPADecodeContext;
+
+/* XXX: suppress that mess */
+struct mpstr *gmp;
+GetBitContext *gmp_gb;
+static MPADecodeContext *gmp_s;
+
+/* XXX: merge constants with encoder */
+static const unsigned short mp_bitrate_tab[2][3][15] = {
+    { {0, 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384, 416, 448 },
+      {0, 32, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 384 },
+      {0, 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320 } },
+    { {0, 32, 48, 56, 64, 80, 96, 112, 128, 144, 160, 176, 192, 224, 256},
+      {0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160},
+      {0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160}
+    }
+};
+
+static unsigned short mp_freq_tab[3] = { 44100, 48000, 32000 };
+
+static int decode_init(AVCodecContext * avctx)
+{
+    MPADecodeContext *s = avctx->priv_data;
+    struct mpstr *mp = &s->mpstr;
+    static int init;
+
+    mp->fr.single = -1;
+    mp->synth_bo = 1;
+
+    if(!init) {
+        init = 1;
+        make_decode_tables(32767);
+        init_layer2();
+        init_layer3(SBLIMIT);
+    }
+
+    s->inbuf_index = 0;
+    s->inbuf = &s->inbuf1[s->inbuf_index][BACKSTEP_SIZE];
+    s->inbuf_ptr = s->inbuf;
+    
+    return 0;
+}
+
+/* fast header check for resync */
+static int check_header(UINT32 header)
+{
+    /* header */
+    if ((header & 0xffe00000) != 0xffe00000)
+	return -1;
+    /* layer check */
+    if (((header >> 17) & 3) == 0)
+	return -1;
+    /* bit rate : currently no free format supported */
+    if (((header >> 12) & 0xf) == 0xf ||
+        ((header >> 12) & 0xf) == 0x0)
+	return -1;
+    /* frequency */
+    if (((header >> 10) & 3) == 3)
+	return -1;
+    return 0;
+}
+
+/* header decoding. MUST check the header before because no
+   consistency check is done there */
+static void decode_header(MPADecodeContext *s, UINT32 header)
+{
+    struct frame *fr = &s->mpstr.fr;
+    int sample_rate, frame_size;
+
+    if (header & (1<<20)) {
+        fr->lsf = (header & (1<<19)) ? 0 : 1;
+        fr->mpeg25 = 0;
+    } else {
+        fr->lsf = 1;
+        fr->mpeg25 = 1;
+    }
+    
+    s->layer = 4 - ((header >> 17) & 3);
+    /* extract frequency */
+    fr->sampling_frequency = ((header >> 10) & 3);
+    sample_rate = mp_freq_tab[fr->sampling_frequency] >> (fr->lsf + fr->mpeg25);
+    fr->sampling_frequency += 3 * (fr->lsf + fr->mpeg25);
+
+    s->error_protection = ((header>>16) & 1) ^ 1;
+
+    fr->bitrate_index = ((header>>12)&0xf);
+    fr->padding   = ((header>>9)&0x1);
+    fr->extension = ((header>>8)&0x1);
+    fr->mode      = ((header>>6)&0x3);
+    fr->mode_ext  = ((header>>4)&0x3);
+    fr->copyright = ((header>>3)&0x1);
+    fr->original  = ((header>>2)&0x1);
+    fr->emphasis  = header & 0x3;
+
+    fr->stereo    = (fr->mode == MPG_MD_MONO) ? 1 : 2;
+
+    
+    frame_size = mp_bitrate_tab[fr->lsf][s->layer - 1][fr->bitrate_index];
+    s->bit_rate = frame_size * 1000;
+    switch(s->layer) {
+    case 1:
+        frame_size = (frame_size * 12000) / sample_rate;
+        frame_size = ((frame_size + fr->padding) << 2);
+        break;
+    case 2:
+        frame_size = (frame_size * 144000) / sample_rate;
+        frame_size += fr->padding;
+        break;
+    case 3:
+        frame_size = (frame_size * 144000) / (sample_rate << fr->lsf);
+        frame_size += fr->padding;
+        break;
+    }
+    s->frame_size = frame_size;
+    s->sample_rate = sample_rate;
+
+#if 0
+    printf("layer%d, %d Hz, %d kbits/s, %s\n",
+           s->layer, s->sample_rate, s->bit_rate, fr->stereo ? "stereo" : "mono");
+#endif
+}
+
+static int mp_decode_frame(MPADecodeContext *s, 
+                           short *samples)
+{
+    int nb_bytes;
+    
+    init_get_bits(&s->gb, s->inbuf + HEADER_SIZE, s->inbuf_ptr - s->inbuf - HEADER_SIZE);
+    
+    /* skip error protection field */
+    if (s->error_protection)
+        get_bits(&s->gb, 16);
+
+    /* XXX: horrible: global! */
+    gmp = &s->mpstr;
+    gmp_s = s;
+    gmp_gb = &s->gb;
+
+    nb_bytes = 0;
+    switch(s->layer) {
+    case 1:
+        do_layer1(&s->mpstr.fr,(unsigned char *)samples, &nb_bytes);
+        break;
+    case 2:
+        do_layer2(&s->mpstr.fr,(unsigned char *)samples, &nb_bytes);
+        break;
+    case 3:
+        do_layer3(&s->mpstr.fr,(unsigned char *)samples, &nb_bytes);
+        s->inbuf_index ^= 1;
+        s->inbuf = &s->inbuf1[s->inbuf_index][BACKSTEP_SIZE];
+        s->old_frame_size = s->frame_size;
+        break;
+    default:
+        break;
+    }
+    return nb_bytes;
+}
+
+/*
+ * seek back in the stream for backstep bytes (at most 511 bytes, and
+ * at most in last frame). Note that this is slightly incorrect (data
+ * can span more than one block!)  
+ */
+int set_pointer(long backstep)
+{
+    UINT8 *ptr;
+
+    /* compute current position in stream */
+    ptr = gmp_gb->buf_ptr - (gmp_gb->bit_cnt >> 3);
+    /* copy old data before current one */
+    ptr -= backstep;
+    memcpy(ptr, gmp_s->inbuf1[gmp_s->inbuf_index ^ 1] + 
+           BACKSTEP_SIZE + gmp_s->old_frame_size - backstep, backstep);
+    /* init get bits again */
+    init_get_bits(gmp_gb, ptr, gmp_s->frame_size + backstep);
+
+    return 0;
+}
+
+static int decode_frame(AVCodecContext * avctx,
+			void *data, int *data_size,
+			UINT8 * buf, int buf_size)
+{
+    MPADecodeContext *s = avctx->priv_data;
+    UINT32 header;
+    UINT8 *buf_ptr;
+    int len, out_size;
+    short *out_samples = data;
+
+    *data_size = 0;
+    buf_ptr = buf;
+    while (buf_size > 0) {
+	len = s->inbuf_ptr - s->inbuf;
+	if (s->frame_size == 0) {
+	    /* no header seen : find one. We need at least 7 bytes to parse it */
+	    len = HEADER_SIZE - len;
+	    if (len > buf_size)
+		len = buf_size;
+	    memcpy(s->inbuf_ptr, buf_ptr, len);
+	    buf_ptr += len;
+	    s->inbuf_ptr += len;
+	    buf_size -= len;
+	    if ((s->inbuf_ptr - s->inbuf) == HEADER_SIZE) {
+		header = (s->inbuf[0] << 24) | (s->inbuf[1] << 16) |
+		    (s->inbuf[2] << 8) | s->inbuf[3];
+		if (check_header(header) < 0) {
+		    /* no sync found : move by one byte (inefficient, but simple!) */
+		    memcpy(s->inbuf, s->inbuf + 1, HEADER_SIZE - 1);
+		    s->inbuf_ptr--;
+		} else {
+		    decode_header(s, header);
+		    /* update codec info */
+		    avctx->sample_rate = s->sample_rate;
+                    avctx->channels = s->mpstr.fr.stereo ? 2 : 1;
+		    avctx->bit_rate = s->bit_rate;
+		}
+	    }
+	} else if (len < s->frame_size) {
+	    len = s->frame_size - len;
+	    if (len > buf_size)
+		len = buf_size;
+
+	    memcpy(s->inbuf_ptr, buf_ptr, len);
+	    buf_ptr += len;
+	    s->inbuf_ptr += len;
+	    buf_size -= len;
+	} else {
+            out_size = mp_decode_frame(s, out_samples);
+	    s->inbuf_ptr = s->inbuf;
+	    s->frame_size = 0;
+	    *data_size = out_size;
+	    break;
+	}
+    }
+    return buf_ptr - buf;
+}
+
+AVCodec mp3_decoder =
+{
+    "mpegaudio",
+    CODEC_TYPE_AUDIO,
+    CODEC_ID_MP2,
+    sizeof(MPADecodeContext),
+    decode_init,
+    NULL,
+    NULL,
+    decode_frame,
+};