1/*
2 * Copyright (c) 2018 Paul B Mahol
3 *
4 * This file is part of FFmpeg.
5 *
6 * FFmpeg is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
10 *
11 * FFmpeg is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
14 * Lesser General Public License for more details.
15 *
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with FFmpeg; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19 */
20
21#include "bsf.h"
22#include "bsf_internal.h"
23#include "get_bits.h"
24#include "mlp_parse.h"
25#include "mlp.h"
26
27typedef struct AccessUnit {
28    uint8_t bits[4];
29    uint16_t offset;
30    uint16_t optional;
31} AccessUnit;
32
33typedef struct TrueHDCoreContext {
34    MLPHeaderInfo hdr;
35} TrueHDCoreContext;
36
37static int truehd_core_filter(AVBSFContext *ctx, AVPacket *pkt)
38{
39    TrueHDCoreContext *s = ctx->priv_data;
40    GetBitContext gbc;
41    AccessUnit units[MAX_SUBSTREAMS];
42    int ret, i, last_offset = 0;
43    int in_size, out_size;
44    int have_header = 0;
45    int substream_bytes = 0;
46    int end;
47
48    ret = ff_bsf_get_packet_ref(ctx, pkt);
49    if (ret < 0)
50        return ret;
51
52    if (pkt->size < 4) {
53        ret = AVERROR_INVALIDDATA;
54        goto fail;
55    }
56
57    in_size = (AV_RB16(pkt->data) & 0xFFF) * 2;
58    if (in_size < 4 || in_size > pkt->size) {
59        ret = AVERROR_INVALIDDATA;
60        goto fail;
61    }
62
63    ret = init_get_bits8(&gbc, pkt->data + 4, pkt->size - 4);
64    if (ret < 0)
65        goto fail;
66
67    if (show_bits_long(&gbc, 32) == 0xf8726fba) {
68        if ((ret = ff_mlp_read_major_sync(ctx, &s->hdr, &gbc)) < 0)
69            goto fail;
70        have_header = 1;
71    }
72
73    if (s->hdr.num_substreams > MAX_SUBSTREAMS) {
74        ret = AVERROR_INVALIDDATA;
75        goto fail;
76    }
77
78    for (i = 0; i < s->hdr.num_substreams; i++) {
79        for (int j = 0; j < 4; j++)
80            units[i].bits[j] = get_bits1(&gbc);
81
82        units[i].offset = get_bits(&gbc, 12);
83        if (i < 3) {
84            last_offset = units[i].offset * 2;
85            substream_bytes += 2;
86        }
87
88        if (units[i].bits[0]) {
89            units[i].optional = get_bits(&gbc, 16);
90            if (i < 3)
91                substream_bytes += 2;
92        }
93    }
94    end = get_bits_count(&gbc) >> 3;
95
96    out_size = end + 4 + last_offset;
97    if (out_size < in_size) {
98        int bpos = 0, reduce = end - have_header * 28 - substream_bytes;
99        uint16_t parity_nibble, dts = AV_RB16(pkt->data + 2);
100        uint16_t auheader;
101        uint8_t header[28];
102
103        av_assert1(reduce >= 0 && reduce % 2 == 0);
104
105        if (have_header) {
106            memcpy(header, pkt->data + 4, 28);
107            header[16]  = (header[16] & 0x0c) | (FFMIN(s->hdr.num_substreams, 3) << 4);
108            header[17] &= 0x7f;
109            header[25] &= 0xfe;
110            AV_WL16(header + 26, ff_mlp_checksum16(header, 26));
111        }
112
113        pkt->data += reduce;
114        out_size  -= reduce;
115        pkt->size  = out_size;
116
117        ret = av_packet_make_writable(pkt);
118        if (ret < 0)
119            goto fail;
120
121        AV_WB16(pkt->data + 2, dts);
122        parity_nibble = dts;
123        parity_nibble ^= out_size / 2;
124
125        for (i = 0; i < FFMIN(s->hdr.num_substreams, 3); i++) {
126            uint16_t substr_hdr = 0;
127
128            substr_hdr |= (units[i].bits[0] << 15);
129            substr_hdr |= (units[i].bits[1] << 14);
130            substr_hdr |= (units[i].bits[2] << 13);
131            substr_hdr |= (units[i].bits[3] << 12);
132            substr_hdr |=  units[i].offset;
133
134            AV_WB16(pkt->data + have_header * 28 + 4 + bpos, substr_hdr);
135
136            parity_nibble ^= substr_hdr;
137            bpos          += 2;
138
139            if (units[i].bits[0]) {
140                AV_WB16(pkt->data + have_header * 28 + 4 + bpos, units[i].optional);
141
142                parity_nibble ^= units[i].optional;
143                bpos          += 2;
144            }
145        }
146
147        parity_nibble ^= parity_nibble >> 8;
148        parity_nibble ^= parity_nibble >> 4;
149        parity_nibble &= 0xF;
150
151        auheader  = (parity_nibble ^ 0xF) << 12;
152        auheader |= (out_size / 2) & 0x0fff;
153        AV_WB16(pkt->data, auheader);
154
155        if (have_header)
156            memcpy(pkt->data + 4, header, 28);
157    }
158
159fail:
160    if (ret < 0)
161        av_packet_unref(pkt);
162
163    return ret;
164}
165
166static void truehd_core_flush(AVBSFContext *ctx)
167{
168    TrueHDCoreContext *s = ctx->priv_data;
169    memset(&s->hdr, 0, sizeof(s->hdr));
170}
171
172static const enum AVCodecID codec_ids[] = {
173    AV_CODEC_ID_TRUEHD, AV_CODEC_ID_NONE,
174};
175
176const FFBitStreamFilter ff_truehd_core_bsf = {
177    .p.name         = "truehd_core",
178    .p.codec_ids    = codec_ids,
179    .priv_data_size = sizeof(TrueHDCoreContext),
180    .filter         = truehd_core_filter,
181    .flush          = truehd_core_flush,
182};
183