1/*
2 * MLP parser
3 * Copyright (c) 2007 Ian Caulfield
4 *
5 * This file is part of FFmpeg.
6 *
7 * FFmpeg is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
11 *
12 * FFmpeg is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 */
21
22/**
23 * @file libavcodec/mlp_parser.c
24 * MLP parser
25 */
26
27#include <stdint.h>
28
29#include "libavutil/crc.h"
30#include "bitstream.h"
31#include "parser.h"
32#include "mlp_parser.h"
33#include "mlp.h"
34
35static const uint8_t mlp_quants[16] = {
36    16, 20, 24, 0, 0, 0, 0, 0,
37     0,  0,  0, 0, 0, 0, 0, 0,
38};
39
40static const uint8_t mlp_channels[32] = {
41    1, 2, 3, 4, 3, 4, 5, 3, 4, 5, 4, 5, 6, 4, 5, 4,
42    5, 6, 5, 5, 6, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
43};
44
45static const uint8_t thd_chancount[13] = {
46//  LR    C   LFE  LRs LRvh  LRc LRrs  Cs   Ts  LRsd  LRw  Cvh  LFE2
47     2,   1,   1,   2,   2,   2,   2,   1,   1,   2,   2,   1,   1
48};
49
50static int mlp_samplerate(int in)
51{
52    if (in == 0xF)
53        return 0;
54
55    return (in & 8 ? 44100 : 48000) << (in & 7) ;
56}
57
58static int truehd_channels(int chanmap)
59{
60    int channels = 0, i;
61
62    for (i = 0; i < 13; i++)
63        channels += thd_chancount[i] * ((chanmap >> i) & 1);
64
65    return channels;
66}
67
68/** Read a major sync info header - contains high level information about
69 *  the stream - sample rate, channel arrangement etc. Most of this
70 *  information is not actually necessary for decoding, only for playback.
71 *  gb must be a freshly initialized GetBitContext with no bits read.
72 */
73
74int ff_mlp_read_major_sync(void *log, MLPHeaderInfo *mh, GetBitContext *gb)
75{
76    int ratebits;
77    uint16_t checksum;
78
79    assert(get_bits_count(gb) == 0);
80
81    if (gb->size_in_bits < 28 << 3) {
82        av_log(log, AV_LOG_ERROR, "packet too short, unable to read major sync\n");
83        return -1;
84    }
85
86    checksum = ff_mlp_checksum16(gb->buffer, 26);
87    if (checksum != AV_RL16(gb->buffer+26)) {
88        av_log(log, AV_LOG_ERROR, "major sync info header checksum error\n");
89        return -1;
90    }
91
92    if (get_bits_long(gb, 24) != 0xf8726f) /* Sync words */
93        return -1;
94
95    mh->stream_type = get_bits(gb, 8);
96
97    if (mh->stream_type == 0xbb) {
98        mh->group1_bits = mlp_quants[get_bits(gb, 4)];
99        mh->group2_bits = mlp_quants[get_bits(gb, 4)];
100
101        ratebits = get_bits(gb, 4);
102        mh->group1_samplerate = mlp_samplerate(ratebits);
103        mh->group2_samplerate = mlp_samplerate(get_bits(gb, 4));
104
105        skip_bits(gb, 11);
106
107        mh->channels_mlp = get_bits(gb, 5);
108    } else if (mh->stream_type == 0xba) {
109        mh->group1_bits = 24; // TODO: Is this information actually conveyed anywhere?
110        mh->group2_bits = 0;
111
112        ratebits = get_bits(gb, 4);
113        mh->group1_samplerate = mlp_samplerate(ratebits);
114        mh->group2_samplerate = 0;
115
116        skip_bits(gb, 8);
117
118        mh->channels_thd_stream1 = get_bits(gb, 5);
119
120        skip_bits(gb, 2);
121
122        mh->channels_thd_stream2 = get_bits(gb, 13);
123    } else
124        return -1;
125
126    mh->access_unit_size = 40 << (ratebits & 7);
127    mh->access_unit_size_pow2 = 64 << (ratebits & 7);
128
129    skip_bits_long(gb, 48);
130
131    mh->is_vbr = get_bits1(gb);
132
133    mh->peak_bitrate = (get_bits(gb, 15) * mh->group1_samplerate + 8) >> 4;
134
135    mh->num_substreams = get_bits(gb, 4);
136
137    skip_bits_long(gb, 4 + 11 * 8);
138
139    return 0;
140}
141
142typedef struct MLPParseContext
143{
144    ParseContext pc;
145
146    int bytes_left;
147
148    int in_sync;
149
150    int num_substreams;
151} MLPParseContext;
152
153static av_cold int mlp_init(AVCodecParserContext *s)
154{
155    ff_mlp_init_crc();
156    return 0;
157}
158
159static int mlp_parse(AVCodecParserContext *s,
160                     AVCodecContext *avctx,
161                     const uint8_t **poutbuf, int *poutbuf_size,
162                     const uint8_t *buf, int buf_size)
163{
164    MLPParseContext *mp = s->priv_data;
165    int sync_present;
166    uint8_t parity_bits;
167    int next;
168    int i, p = 0;
169
170    *poutbuf_size = 0;
171    if (buf_size == 0)
172        return 0;
173
174    if (!mp->in_sync) {
175        // Not in sync - find a major sync header
176
177        for (i = 0; i < buf_size; i++) {
178            mp->pc.state = (mp->pc.state << 8) | buf[i];
179            if ((mp->pc.state & 0xfffffffe) == 0xf8726fba) {
180                mp->in_sync = 1;
181                mp->bytes_left = 0;
182                break;
183            }
184        }
185
186        if (!mp->in_sync) {
187            ff_combine_frame(&mp->pc, END_NOT_FOUND, &buf, &buf_size);
188            return buf_size;
189        }
190
191        ff_combine_frame(&mp->pc, i - 7, &buf, &buf_size);
192
193        return i - 7;
194    }
195
196    if (mp->bytes_left == 0) {
197        // Find length of this packet
198
199        /* Copy overread bytes from last frame into buffer. */
200        for(; mp->pc.overread>0; mp->pc.overread--) {
201            mp->pc.buffer[mp->pc.index++]= mp->pc.buffer[mp->pc.overread_index++];
202        }
203
204        if (mp->pc.index + buf_size < 2) {
205            ff_combine_frame(&mp->pc, END_NOT_FOUND, &buf, &buf_size);
206            return buf_size;
207        }
208
209        mp->bytes_left = ((mp->pc.index > 0 ? mp->pc.buffer[0] : buf[0]) << 8)
210                       |  (mp->pc.index > 1 ? mp->pc.buffer[1] : buf[1-mp->pc.index]);
211        mp->bytes_left = (mp->bytes_left & 0xfff) * 2;
212        mp->bytes_left -= mp->pc.index;
213    }
214
215    next = (mp->bytes_left > buf_size) ? END_NOT_FOUND : mp->bytes_left;
216
217    if (ff_combine_frame(&mp->pc, next, &buf, &buf_size) < 0) {
218        mp->bytes_left -= buf_size;
219        return buf_size;
220    }
221
222    mp->bytes_left = 0;
223
224    sync_present = (AV_RB32(buf + 4) & 0xfffffffe) == 0xf8726fba;
225
226    if (!sync_present) {
227        /* The first nibble of a frame is a parity check of the 4-byte
228         * access unit header and all the 2- or 4-byte substream headers. */
229        // Only check when this isn't a sync frame - syncs have a checksum.
230
231        parity_bits = 0;
232        for (i = -1; i < mp->num_substreams; i++) {
233            parity_bits ^= buf[p++];
234            parity_bits ^= buf[p++];
235
236            if (i < 0 || buf[p-2] & 0x80) {
237                parity_bits ^= buf[p++];
238                parity_bits ^= buf[p++];
239            }
240        }
241
242        if ((((parity_bits >> 4) ^ parity_bits) & 0xF) != 0xF) {
243            av_log(avctx, AV_LOG_INFO, "mlpparse: Parity check failed.\n");
244            goto lost_sync;
245        }
246    } else {
247        GetBitContext gb;
248        MLPHeaderInfo mh;
249
250        init_get_bits(&gb, buf + 4, (buf_size - 4) << 3);
251        if (ff_mlp_read_major_sync(avctx, &mh, &gb) < 0)
252            goto lost_sync;
253
254        avctx->bits_per_raw_sample = mh.group1_bits;
255        if (avctx->bits_per_raw_sample > 16)
256            avctx->sample_fmt = SAMPLE_FMT_S32;
257        else
258            avctx->sample_fmt = SAMPLE_FMT_S16;
259        avctx->sample_rate = mh.group1_samplerate;
260        avctx->frame_size = mh.access_unit_size;
261
262        if (mh.stream_type == 0xbb) {
263            /* MLP stream */
264            avctx->channels = mlp_channels[mh.channels_mlp];
265        } else { /* mh.stream_type == 0xba */
266            /* TrueHD stream */
267            if (mh.channels_thd_stream2)
268                avctx->channels = truehd_channels(mh.channels_thd_stream2);
269            else
270                avctx->channels = truehd_channels(mh.channels_thd_stream1);
271        }
272
273        if (!mh.is_vbr) /* Stream is CBR */
274            avctx->bit_rate = mh.peak_bitrate;
275
276        mp->num_substreams = mh.num_substreams;
277    }
278
279    *poutbuf = buf;
280    *poutbuf_size = buf_size;
281
282    return next;
283
284lost_sync:
285    mp->in_sync = 0;
286    return 1;
287}
288
289AVCodecParser mlp_parser = {
290    { CODEC_ID_MLP },
291    sizeof(MLPParseContext),
292    mlp_init,
293    mlp_parse,
294    NULL,
295};
296