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/*
* RTP Depacketization of Opus, RFC 7587
* Copyright (c) 2025 Jonathan Baudanza <jon@jonb.org>
* Copyright (c) 2022 Erik Linge
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "libavcodec/bytestream.h"
#include "libavutil/mem.h"
#include "libavutil/avstring.h"
#include "rtpdec_formats.h"
#include "internal.h"
static int opus_duration(const uint8_t *src, int size)
{
unsigned nb_frames = 1;
unsigned toc = src[0];
unsigned toc_config = toc >> 3;
unsigned toc_count = toc & 3;
unsigned frame_size = toc_config < 12 ? FFMAX(480, 960 * (toc_config & 3)) :
toc_config < 16 ? 480 << (toc_config & 1) :
120 << (toc_config & 3);
if (toc_count == 3) {
if (size<2)
return AVERROR_INVALIDDATA;
nb_frames = src[1] & 0x3F;
} else if (toc_count) {
nb_frames = 2;
}
return frame_size * nb_frames;
}
static int opus_write_extradata(AVCodecParameters *codecpar)
{
uint8_t *bs;
int ret;
/* This function writes an extradata with a channel mapping family of 0.
* This mapping family only supports mono and stereo layouts. And RFC7587
* specifies that the number of channels in the SDP must be 2.
*/
if (codecpar->ch_layout.nb_channels > 2) {
return AVERROR_INVALIDDATA;
}
ret = ff_alloc_extradata(codecpar, 19);
if (ret < 0)
return ret;
bs = (uint8_t *)codecpar->extradata;
/* Opus magic */
bytestream_put_buffer(&bs, "OpusHead", 8);
/* Version */
bytestream_put_byte (&bs, 0x1);
/* Channel count */
bytestream_put_byte (&bs, codecpar->ch_layout.nb_channels);
/* Pre skip */
bytestream_put_le16 (&bs, 0);
/* Input sample rate */
bytestream_put_le32 (&bs, 48000);
/* Output gain */
bytestream_put_le16 (&bs, 0x0);
/* Mapping family */
bytestream_put_byte (&bs, 0x0);
return 0;
}
static int opus_init(AVFormatContext *s, int st_index, PayloadContext *priv_data)
{
return opus_write_extradata(s->streams[st_index]->codecpar);
}
static int opus_parse_packet(AVFormatContext *ctx, PayloadContext *data,
AVStream *st, AVPacket *pkt, uint32_t *timestamp,
const uint8_t *buf, int len, uint16_t seq,
int flags)
{
int rv;
int duration;
if ((rv = av_new_packet(pkt, len)) < 0)
return rv;
memcpy(pkt->data, buf, len);
pkt->stream_index = st->index;
duration = opus_duration(buf, len);
if (duration != AVERROR_INVALIDDATA) {
pkt->duration = duration;
}
return 0;
}
static int parse_fmtp(AVFormatContext *s,
AVStream *stream, PayloadContext *data,
const char *attr, const char *value)
{
if (!strcmp(attr, "sprop-maxcapturerate")) {
int rate = atoi(value);
if (rate < 8000 || rate > 48000) {
av_log(s, AV_LOG_ERROR,
"fmtp field 'sprop-maxcapturerate' must be between 8000 to 48000 (provided value: %s)",
value);
return AVERROR_INVALIDDATA;
}
stream->codecpar->sample_rate = rate;
}
return 0;
}
static int opus_parse_sdp_line(AVFormatContext *s, int st_index,
PayloadContext *data, const char *line)
{
const char *p;
if (st_index < 0)
return 0;
if (av_strstart(line, "fmtp:", &p)) {
return ff_parse_fmtp(s, s->streams[st_index], data, p, parse_fmtp);
}
return 0;
}
const RTPDynamicProtocolHandler ff_opus_dynamic_handler = {
.enc_name = "opus",
.codec_type = AVMEDIA_TYPE_AUDIO,
.codec_id = AV_CODEC_ID_OPUS,
.parse_packet = opus_parse_packet,
.init = opus_init,
.parse_sdp_a_line = opus_parse_sdp_line,
};
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