1/*
2 * MPEG Audio parser
3 * Copyright (c) 2003 Fabrice Bellard
4 * Copyright (c) 2003 Michael Niedermayer
5 *
6 * This file is part of FFmpeg.
7 *
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.
12 *
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.
17 *
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
21 */
22
23#include "parser.h"
24#include "mpegaudio.h"
25#include "mpegaudiodecheader.h"
26
27
28typedef struct MpegAudioParseContext {
29    uint8_t inbuf[MPA_MAX_CODED_FRAME_SIZE];    /* input buffer */
30    uint8_t *inbuf_ptr;
31    int frame_size;
32    int free_format_frame_size;
33    int free_format_next_header;
34    uint32_t header;
35    int header_count;
36} MpegAudioParseContext;
37
38#define MPA_HEADER_SIZE 4
39
40/* header + layer + bitrate + freq + lsf/mpeg25 */
41#undef SAME_HEADER_MASK /* mpegaudio.h defines different version */
42#define SAME_HEADER_MASK \
43   (0xffe00000 | (3 << 17) | (3 << 10) | (3 << 19))
44
45/* useful helper to get mpeg audio stream infos. Return -1 if error in
46   header, otherwise the coded frame size in bytes */
47int ff_mpa_decode_header(AVCodecContext *avctx, uint32_t head, int *sample_rate, int *channels, int *frame_size, int *bit_rate)
48{
49    MPADecodeHeader s1, *s = &s1;
50
51    if (ff_mpa_check_header(head) != 0)
52        return -1;
53
54    if (ff_mpegaudio_decode_header(s, head) != 0) {
55        return -1;
56    }
57
58    switch(s->layer) {
59    case 1:
60        avctx->codec_id = CODEC_ID_MP1;
61        *frame_size = 384;
62        break;
63    case 2:
64        avctx->codec_id = CODEC_ID_MP2;
65        *frame_size = 1152;
66        break;
67    default:
68    case 3:
69        avctx->codec_id = CODEC_ID_MP3;
70        if (s->lsf)
71            *frame_size = 576;
72        else
73            *frame_size = 1152;
74        break;
75    }
76
77    *sample_rate = s->sample_rate;
78    *channels = s->nb_channels;
79    *bit_rate = s->bit_rate;
80    avctx->sub_id = s->layer;
81    return s->frame_size;
82}
83
84static av_cold int mpegaudio_parse_init(AVCodecParserContext *s1)
85{
86    MpegAudioParseContext *s = s1->priv_data;
87    s->inbuf_ptr = s->inbuf;
88    return 0;
89}
90
91static int mpegaudio_parse(AVCodecParserContext *s1,
92                           AVCodecContext *avctx,
93                           const uint8_t **poutbuf, int *poutbuf_size,
94                           const uint8_t *buf, int buf_size)
95{
96    MpegAudioParseContext *s = s1->priv_data;
97    int len, ret, sr, channels, bit_rate, frame_size;
98    uint32_t header;
99    const uint8_t *buf_ptr;
100
101    *poutbuf = NULL;
102    *poutbuf_size = 0;
103    buf_ptr = buf;
104    while (buf_size > 0) {
105        len = s->inbuf_ptr - s->inbuf;
106        if (s->frame_size == 0) {
107            /* special case for next header for first frame in free
108               format case (XXX: find a simpler method) */
109            if (s->free_format_next_header != 0) {
110                AV_WB32(s->inbuf, s->free_format_next_header);
111                s->inbuf_ptr = s->inbuf + 4;
112                s->free_format_next_header = 0;
113                goto got_header;
114            }
115            /* no header seen : find one. We need at least MPA_HEADER_SIZE
116               bytes to parse it */
117            len = FFMIN(MPA_HEADER_SIZE - len, buf_size);
118            if (len > 0) {
119                memcpy(s->inbuf_ptr, buf_ptr, len);
120                buf_ptr += len;
121                buf_size -= len;
122                s->inbuf_ptr += len;
123            }
124            if ((s->inbuf_ptr - s->inbuf) >= MPA_HEADER_SIZE) {
125            got_header:
126                header = AV_RB32(s->inbuf);
127
128                ret = ff_mpa_decode_header(avctx, header, &sr, &channels, &frame_size, &bit_rate);
129                if (ret < 0) {
130                    s->header_count= -2;
131                    /* no sync found : move by one byte (inefficient, but simple!) */
132                    memmove(s->inbuf, s->inbuf + 1, s->inbuf_ptr - s->inbuf - 1);
133                    s->inbuf_ptr--;
134                    dprintf(avctx, "skip %x\n", header);
135                    /* reset free format frame size to give a chance
136                       to get a new bitrate */
137                    s->free_format_frame_size = 0;
138                } else {
139                    if((header&SAME_HEADER_MASK) != (s->header&SAME_HEADER_MASK) && s->header)
140                        s->header_count= -3;
141                    s->header= header;
142                    s->header_count++;
143                    s->frame_size = ret;
144
145#if 0
146                    /* free format: prepare to compute frame size */
147                    if (ff_mpegaudio_decode_header((MPADecodeHeader *)s, header) == 1) {
148                        s->frame_size = -1;
149                    }
150#endif
151                    if(s->header_count > 1){
152                        avctx->sample_rate= sr;
153                        avctx->channels   = channels;
154                        avctx->frame_size = frame_size;
155                        avctx->bit_rate   = bit_rate;
156                    }
157                }
158            }
159        } else
160#if 0
161        if (s->frame_size == -1) {
162            /* free format : find next sync to compute frame size */
163            len = MPA_MAX_CODED_FRAME_SIZE - len;
164            if (len > buf_size)
165                len = buf_size;
166            if (len == 0) {
167                /* frame too long: resync */
168                s->frame_size = 0;
169                memmove(s->inbuf, s->inbuf + 1, s->inbuf_ptr - s->inbuf - 1);
170                s->inbuf_ptr--;
171            } else {
172                uint8_t *p, *pend;
173                uint32_t header1;
174                int padding;
175
176                memcpy(s->inbuf_ptr, buf_ptr, len);
177                /* check for header */
178                p = s->inbuf_ptr - 3;
179                pend = s->inbuf_ptr + len - 4;
180                while (p <= pend) {
181                    header = AV_RB32(p);
182                    header1 = AV_RB32(s->inbuf);
183                    /* check with high probability that we have a
184                       valid header */
185                    if ((header & SAME_HEADER_MASK) ==
186                        (header1 & SAME_HEADER_MASK)) {
187                        /* header found: update pointers */
188                        len = (p + 4) - s->inbuf_ptr;
189                        buf_ptr += len;
190                        buf_size -= len;
191                        s->inbuf_ptr = p;
192                        /* compute frame size */
193                        s->free_format_next_header = header;
194                        s->free_format_frame_size = s->inbuf_ptr - s->inbuf;
195                        padding = (header1 >> 9) & 1;
196                        if (s->layer == 1)
197                            s->free_format_frame_size -= padding * 4;
198                        else
199                            s->free_format_frame_size -= padding;
200                        dprintf(avctx, "free frame size=%d padding=%d\n",
201                                s->free_format_frame_size, padding);
202                        ff_mpegaudio_decode_header((MPADecodeHeader *)s, header1);
203                        goto next_data;
204                    }
205                    p++;
206                }
207                /* not found: simply increase pointers */
208                buf_ptr += len;
209                s->inbuf_ptr += len;
210                buf_size -= len;
211            }
212        } else
213#endif
214        if (len < s->frame_size) {
215            if (s->frame_size > MPA_MAX_CODED_FRAME_SIZE)
216                s->frame_size = MPA_MAX_CODED_FRAME_SIZE;
217            len = FFMIN(s->frame_size - len, buf_size);
218            memcpy(s->inbuf_ptr, buf_ptr, len);
219            buf_ptr += len;
220            s->inbuf_ptr += len;
221            buf_size -= len;
222        }
223
224        if(s->frame_size > 0 && buf_ptr - buf == s->inbuf_ptr - s->inbuf
225           && buf_size + buf_ptr - buf >= s->frame_size){
226            if(s->header_count > 0){
227                *poutbuf = buf;
228                *poutbuf_size = s->frame_size;
229            }
230            buf_ptr = buf + s->frame_size;
231            s->inbuf_ptr = s->inbuf;
232            s->frame_size = 0;
233            break;
234        }
235
236        //    next_data:
237        if (s->frame_size > 0 &&
238            (s->inbuf_ptr - s->inbuf) >= s->frame_size) {
239            if(s->header_count > 0){
240                *poutbuf = s->inbuf;
241                *poutbuf_size = s->inbuf_ptr - s->inbuf;
242            }
243            s->inbuf_ptr = s->inbuf;
244            s->frame_size = 0;
245            break;
246        }
247    }
248    return buf_ptr - buf;
249}
250
251
252AVCodecParser mpegaudio_parser = {
253    { CODEC_ID_MP1, CODEC_ID_MP2, CODEC_ID_MP3 },
254    sizeof(MpegAudioParseContext),
255    mpegaudio_parse_init,
256    mpegaudio_parse,
257    NULL,
258};
259