3 * Copyright (c) 2003 Fabrice Bellard.
4 * Copyright (c) 2003 Michael Niedermayer.
6 * This file is part of FFmpeg.
8 * FFmpeg is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; either
11 * version 2.1 of the License, or (at your option) any later version.
13 * FFmpeg is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Lesser General Public License for more details.
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with FFmpeg; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
24 #include "mpegaudio.h"
27 typedef struct MpegAudioParseContext {
28 uint8_t inbuf[MPA_MAX_CODED_FRAME_SIZE]; /* input buffer */
31 int free_format_frame_size;
32 int free_format_next_header;
35 } MpegAudioParseContext;
37 #define MPA_HEADER_SIZE 4
39 /* header + layer + bitrate + freq + lsf/mpeg25 */
40 #undef SAME_HEADER_MASK /* mpegaudio.h defines different version */
41 #define SAME_HEADER_MASK \
42 (0xffe00000 | (3 << 17) | (3 << 10) | (3 << 19))
44 static int mpegaudio_parse_init(AVCodecParserContext *s1)
46 MpegAudioParseContext *s = s1->priv_data;
47 s->inbuf_ptr = s->inbuf;
51 static int mpegaudio_parse(AVCodecParserContext *s1,
52 AVCodecContext *avctx,
53 uint8_t **poutbuf, int *poutbuf_size,
54 const uint8_t *buf, int buf_size)
56 MpegAudioParseContext *s = s1->priv_data;
59 const uint8_t *buf_ptr;
64 while (buf_size > 0) {
65 len = s->inbuf_ptr - s->inbuf;
66 if (s->frame_size == 0) {
67 /* special case for next header for first frame in free
68 format case (XXX: find a simpler method) */
69 if (s->free_format_next_header != 0) {
70 s->inbuf[0] = s->free_format_next_header >> 24;
71 s->inbuf[1] = s->free_format_next_header >> 16;
72 s->inbuf[2] = s->free_format_next_header >> 8;
73 s->inbuf[3] = s->free_format_next_header;
74 s->inbuf_ptr = s->inbuf + 4;
75 s->free_format_next_header = 0;
78 /* no header seen : find one. We need at least MPA_HEADER_SIZE
80 len = FFMIN(MPA_HEADER_SIZE - len, buf_size);
82 memcpy(s->inbuf_ptr, buf_ptr, len);
87 if ((s->inbuf_ptr - s->inbuf) >= MPA_HEADER_SIZE) {
89 header = (s->inbuf[0] << 24) | (s->inbuf[1] << 16) |
90 (s->inbuf[2] << 8) | s->inbuf[3];
92 ret = mpa_decode_header(avctx, header, &sr);
95 /* no sync found : move by one byte (inefficient, but simple!) */
96 memmove(s->inbuf, s->inbuf + 1, s->inbuf_ptr - s->inbuf - 1);
98 dprintf(avctx, "skip %x\n", header);
99 /* reset free format frame size to give a chance
100 to get a new bitrate */
101 s->free_format_frame_size = 0;
103 if((header&SAME_HEADER_MASK) != (s->header&SAME_HEADER_MASK) && s->header)
110 /* free format: prepare to compute frame size */
111 if (decode_header(s, header) == 1) {
116 if(s->header_count > 1)
117 avctx->sample_rate= sr;
121 if (s->frame_size == -1) {
122 /* free format : find next sync to compute frame size */
123 len = MPA_MAX_CODED_FRAME_SIZE - len;
127 /* frame too long: resync */
129 memmove(s->inbuf, s->inbuf + 1, s->inbuf_ptr - s->inbuf - 1);
136 memcpy(s->inbuf_ptr, buf_ptr, len);
137 /* check for header */
138 p = s->inbuf_ptr - 3;
139 pend = s->inbuf_ptr + len - 4;
141 header = (p[0] << 24) | (p[1] << 16) |
143 header1 = (s->inbuf[0] << 24) | (s->inbuf[1] << 16) |
144 (s->inbuf[2] << 8) | s->inbuf[3];
145 /* check with high probability that we have a
147 if ((header & SAME_HEADER_MASK) ==
148 (header1 & SAME_HEADER_MASK)) {
149 /* header found: update pointers */
150 len = (p + 4) - s->inbuf_ptr;
154 /* compute frame size */
155 s->free_format_next_header = header;
156 s->free_format_frame_size = s->inbuf_ptr - s->inbuf;
157 padding = (header1 >> 9) & 1;
159 s->free_format_frame_size -= padding * 4;
161 s->free_format_frame_size -= padding;
162 dprintf(avctx, "free frame size=%d padding=%d\n",
163 s->free_format_frame_size, padding);
164 decode_header(s, header1);
169 /* not found: simply increase pointers */
176 if (len < s->frame_size) {
177 if (s->frame_size > MPA_MAX_CODED_FRAME_SIZE)
178 s->frame_size = MPA_MAX_CODED_FRAME_SIZE;
179 len = FFMIN(s->frame_size - len, buf_size);
180 memcpy(s->inbuf_ptr, buf_ptr, len);
186 if(s->frame_size > 0 && buf_ptr - buf == s->inbuf_ptr - s->inbuf
187 && buf_size + buf_ptr - buf >= s->frame_size){
188 if(s->header_count > 0){
190 *poutbuf_size = s->frame_size;
192 buf_ptr = buf + s->frame_size;
193 s->inbuf_ptr = s->inbuf;
199 if (s->frame_size > 0 &&
200 (s->inbuf_ptr - s->inbuf) >= s->frame_size) {
201 if(s->header_count > 0){
203 *poutbuf_size = s->inbuf_ptr - s->inbuf;
205 s->inbuf_ptr = s->inbuf;
210 return buf_ptr - buf;
214 AVCodecParser mpegaudio_parser = {
215 { CODEC_ID_MP2, CODEC_ID_MP3 },
216 sizeof(MpegAudioParseContext),
217 mpegaudio_parse_init,