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path: root/libavformat/latmenc.c (plain)
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1/*
2 * LATM/LOAS muxer
3 * Copyright (c) 2011 Kieran Kunhya <kieran@kunhya.com>
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#include "libavcodec/get_bits.h"
23#include "libavcodec/put_bits.h"
24#include "libavcodec/avcodec.h"
25#include "libavcodec/mpeg4audio.h"
26#include "libavutil/opt.h"
27#include "avformat.h"
28#include "internal.h"
29#include "rawenc.h"
30
31#define MAX_EXTRADATA_SIZE 1024
32
33typedef struct LATMContext {
34 AVClass *av_class;
35 int off;
36 int channel_conf;
37 int object_type;
38 int counter;
39 int mod;
40 uint8_t buffer[0x1fff + MAX_EXTRADATA_SIZE + 1024];
41} LATMContext;
42
43static const AVOption options[] = {
44 {"smc-interval", "StreamMuxConfig interval.",
45 offsetof(LATMContext, mod), AV_OPT_TYPE_INT, {.i64 = 0x0014}, 0x0001, 0xffff, AV_OPT_FLAG_ENCODING_PARAM},
46 {NULL},
47};
48
49static const AVClass latm_muxer_class = {
50 .class_name = "LATM/LOAS muxer",
51 .item_name = av_default_item_name,
52 .option = options,
53 .version = LIBAVUTIL_VERSION_INT,
54};
55
56static int latm_decode_extradata(LATMContext *ctx, uint8_t *buf, int size)
57{
58 MPEG4AudioConfig m4ac;
59
60 if (size > MAX_EXTRADATA_SIZE) {
61 av_log(ctx, AV_LOG_ERROR, "Extradata is larger than currently supported.\n");
62 return AVERROR_INVALIDDATA;
63 }
64 ctx->off = avpriv_mpeg4audio_get_config(&m4ac, buf, size * 8, 1);
65 if (ctx->off < 0)
66 return ctx->off;
67
68 if (ctx->object_type == AOT_ALS && (ctx->off & 7)) {
69 // as long as avpriv_mpeg4audio_get_config works correctly this is impossible
70 av_log(ctx, AV_LOG_ERROR, "BUG: ALS offset is not byte-aligned\n");
71 return AVERROR_INVALIDDATA;
72 }
73 /* FIXME: are any formats not allowed in LATM? */
74
75 if (m4ac.object_type > AOT_SBR && m4ac.object_type != AOT_ALS) {
76 av_log(ctx, AV_LOG_ERROR, "Muxing MPEG-4 AOT %d in LATM is not supported\n", m4ac.object_type);
77 return AVERROR_INVALIDDATA;
78 }
79 ctx->channel_conf = m4ac.chan_config;
80 ctx->object_type = m4ac.object_type;
81
82 return 0;
83}
84
85static int latm_write_header(AVFormatContext *s)
86{
87 LATMContext *ctx = s->priv_data;
88 AVCodecParameters *par = s->streams[0]->codecpar;
89
90 if (par->codec_id == AV_CODEC_ID_AAC_LATM)
91 return 0;
92
93 if (par->extradata_size > 0 &&
94 latm_decode_extradata(ctx, par->extradata, par->extradata_size) < 0)
95 return AVERROR_INVALIDDATA;
96
97 return 0;
98}
99
100static void latm_write_frame_header(AVFormatContext *s, PutBitContext *bs)
101{
102 LATMContext *ctx = s->priv_data;
103 AVCodecParameters *par = s->streams[0]->codecpar;
104 int header_size;
105
106 /* AudioMuxElement */
107 put_bits(bs, 1, !!ctx->counter);
108
109 if (!ctx->counter) {
110 /* StreamMuxConfig */
111 put_bits(bs, 1, 0); /* audioMuxVersion */
112 put_bits(bs, 1, 1); /* allStreamsSameTimeFraming */
113 put_bits(bs, 6, 0); /* numSubFrames */
114 put_bits(bs, 4, 0); /* numProgram */
115 put_bits(bs, 3, 0); /* numLayer */
116
117 /* AudioSpecificConfig */
118 if (ctx->object_type == AOT_ALS) {
119 header_size = par->extradata_size-(ctx->off >> 3);
120 avpriv_copy_bits(bs, &par->extradata[ctx->off >> 3], header_size);
121 } else {
122 // + 3 assumes not scalable and dependsOnCoreCoder == 0,
123 // see decode_ga_specific_config in libavcodec/aacdec.c
124 avpriv_copy_bits(bs, par->extradata, ctx->off + 3);
125
126 if (!ctx->channel_conf) {
127 GetBitContext gb;
128 int ret = init_get_bits8(&gb, par->extradata, par->extradata_size);
129 av_assert0(ret >= 0); // extradata size has been checked already, so this should not fail
130 skip_bits_long(&gb, ctx->off + 3);
131 avpriv_copy_pce_data(bs, &gb);
132 }
133 }
134
135 put_bits(bs, 3, 0); /* frameLengthType */
136 put_bits(bs, 8, 0xff); /* latmBufferFullness */
137
138 put_bits(bs, 1, 0); /* otherDataPresent */
139 put_bits(bs, 1, 0); /* crcCheckPresent */
140 }
141
142 ctx->counter++;
143 ctx->counter %= ctx->mod;
144}
145
146static int latm_write_packet(AVFormatContext *s, AVPacket *pkt)
147{
148 LATMContext *ctx = s->priv_data;
149 AVIOContext *pb = s->pb;
150 PutBitContext bs;
151 int i, len;
152 uint8_t loas_header[] = "\x56\xe0\x00";
153
154 if (s->streams[0]->codecpar->codec_id == AV_CODEC_ID_AAC_LATM)
155 return ff_raw_write_packet(s, pkt);
156
157 if (!s->streams[0]->codecpar->extradata) {
158 if(pkt->size > 2 && pkt->data[0] == 0x56 && (pkt->data[1] >> 4) == 0xe &&
159 (AV_RB16(pkt->data + 1) & 0x1FFF) + 3 == pkt->size)
160 return ff_raw_write_packet(s, pkt);
161 else
162 return AVERROR_INVALIDDATA;
163 }
164
165 if (pkt->size > 0x1fff)
166 goto too_large;
167
168 init_put_bits(&bs, ctx->buffer, pkt->size+1024+MAX_EXTRADATA_SIZE);
169
170 latm_write_frame_header(s, &bs);
171
172 /* PayloadLengthInfo() */
173 for (i = 0; i <= pkt->size-255; i+=255)
174 put_bits(&bs, 8, 255);
175
176 put_bits(&bs, 8, pkt->size-i);
177
178 /* The LATM payload is written unaligned */
179
180 /* PayloadMux() */
181 if (pkt->size && (pkt->data[0] & 0xe1) == 0x81) {
182 // Convert byte-aligned DSE to non-aligned.
183 // Due to the input format encoding we know that
184 // it is naturally byte-aligned in the input stream,
185 // so there are no padding bits to account for.
186 // To avoid having to add padding bits and rearrange
187 // the whole stream we just remove the byte-align flag.
188 // This allows us to remux our FATE AAC samples into latm
189 // files that are still playable with minimal effort.
190 put_bits(&bs, 8, pkt->data[0] & 0xfe);
191 avpriv_copy_bits(&bs, pkt->data + 1, 8*pkt->size - 8);
192 } else
193 avpriv_copy_bits(&bs, pkt->data, 8*pkt->size);
194
195 avpriv_align_put_bits(&bs);
196 flush_put_bits(&bs);
197
198 len = put_bits_count(&bs) >> 3;
199
200 if (len > 0x1fff)
201 goto too_large;
202
203 loas_header[1] |= (len >> 8) & 0x1f;
204 loas_header[2] |= len & 0xff;
205
206 avio_write(pb, loas_header, 3);
207 avio_write(pb, ctx->buffer, len);
208
209 return 0;
210
211too_large:
212 av_log(s, AV_LOG_ERROR, "LATM packet size larger than maximum size 0x1fff\n");
213 return AVERROR_INVALIDDATA;
214}
215
216static int latm_check_bitstream(struct AVFormatContext *s, const AVPacket *pkt)
217{
218 int ret = 1;
219 AVStream *st = s->streams[pkt->stream_index];
220
221 if (st->codecpar->codec_id == AV_CODEC_ID_AAC) {
222 if (pkt->size > 2 && (AV_RB16(pkt->data) & 0xfff0) == 0xfff0)
223 ret = ff_stream_add_bitstream_filter(st, "aac_adtstoasc", NULL);
224 }
225
226 return ret;
227}
228
229AVOutputFormat ff_latm_muxer = {
230 .name = "latm",
231 .long_name = NULL_IF_CONFIG_SMALL("LOAS/LATM"),
232 .mime_type = "audio/MP4A-LATM",
233 .extensions = "latm,loas",
234 .priv_data_size = sizeof(LATMContext),
235 .audio_codec = AV_CODEC_ID_AAC,
236 .video_codec = AV_CODEC_ID_NONE,
237 .write_header = latm_write_header,
238 .write_packet = latm_write_packet,
239 .priv_class = &latm_muxer_class,
240 .check_bitstream= latm_check_bitstream,
241 .flags = AVFMT_NOTIMESTAMPS,
242};
243
generated by cgit at 2024-05-17 01:48:44 (GMT)