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/*
* LC3 encoder wrapper
* Copyright (C) 2024 Antoine Soulier <asoulier@google.com>
*
* This file is part of FFmpeg.
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <lc3.h>
#include "libavutil/intreadwrite.h"
#include "libavutil/opt.h"
#include "libavutil/mem.h"
#include "avcodec.h"
#include "codec.h"
#include "codec_internal.h"
#include "encode.h"
#define ENCODER_MAX_CHANNELS 2
typedef struct LibLC3EncOpts {
float frame_duration;
int hr_mode;
} LibLC3EncOpts;
typedef struct LibLC3EncContext {
const AVClass *av_class;
LibLC3EncOpts opts;
int block_bytes;
void *encoder_mem;
lc3_encoder_t encoder[ENCODER_MAX_CHANNELS];
int delay_samples;
int remaining_samples;
} LibLC3EncContext;
static av_cold int liblc3_encode_init(AVCodecContext *avctx)
{
LibLC3EncContext *liblc3 = avctx->priv_data;
bool hr_mode = liblc3->opts.hr_mode;
int frame_us = liblc3->opts.frame_duration * 1000;
int srate_hz = avctx->sample_rate;
int channels = avctx->ch_layout.nb_channels;
int effective_bit_rate;
unsigned encoder_size;
if (frame_us != 2500 && frame_us != 5000 &&
frame_us != 7500 && frame_us != 10000 ) {
av_log(avctx, AV_LOG_ERROR,
"Unsupported frame duration %.1f ms.\n", frame_us / 1000.f);
return AVERROR(EINVAL);
}
if (channels < 0 || channels > ENCODER_MAX_CHANNELS) {
av_log(avctx, AV_LOG_ERROR,
"Invalid number of channels %d. Max %d channels are accepted\n",
channels, ENCODER_MAX_CHANNELS);
return AVERROR(EINVAL);
}
hr_mode |= srate_hz > 48000;
hr_mode &= srate_hz >= 48000;
if (frame_us == 7500 && hr_mode) {
av_log(avctx, AV_LOG_ERROR,
"High-resolution mode is not supported with 7.5 ms frames.\n");
return AVERROR(EINVAL);
}
av_log(avctx, AV_LOG_INFO, "Encoding %.1f ms frames.\n", frame_us / 1000.f);
if (hr_mode)
av_log(avctx, AV_LOG_INFO, "High-resolution mode is enabled.\n");
liblc3->block_bytes = lc3_hr_frame_block_bytes(
hr_mode, frame_us, srate_hz, channels, avctx->bit_rate);
effective_bit_rate = lc3_hr_resolve_bitrate(
hr_mode, frame_us, srate_hz, liblc3->block_bytes);
if (avctx->bit_rate != effective_bit_rate)
av_log(avctx, AV_LOG_WARNING,
"Bitrate changed to %d bps.\n", effective_bit_rate);
avctx->bit_rate = effective_bit_rate;
encoder_size = lc3_hr_encoder_size(hr_mode, frame_us, srate_hz);
if (!encoder_size)
return AVERROR(EINVAL);
liblc3->encoder_mem = av_malloc_array(channels, encoder_size);
if (!liblc3->encoder_mem)
return AVERROR(ENOMEM);
for (int ch = 0; ch < channels; ch++) {
liblc3->encoder[ch] = lc3_hr_setup_encoder(
hr_mode, frame_us, srate_hz, 0,
(char *)liblc3->encoder_mem + ch * encoder_size);
}
avctx->extradata = av_mallocz(6 + AV_INPUT_BUFFER_PADDING_SIZE);
if (!avctx->extradata)
return AVERROR(ENOMEM);
AV_WL16(avctx->extradata + 0, frame_us / 10);
AV_WL16(avctx->extradata + 2, 0);
AV_WL16(avctx->extradata + 4, hr_mode);
avctx->extradata_size = 6;
avctx->frame_size = av_rescale(frame_us, srate_hz, 1000*1000);
liblc3->delay_samples = lc3_hr_delay_samples(hr_mode, frame_us, srate_hz);
liblc3->remaining_samples = 0;
return 0;
}
static av_cold int liblc3_encode_close(AVCodecContext *avctx)
{
LibLC3EncContext *liblc3 = avctx->priv_data;
av_freep(&liblc3->encoder_mem);
return 0;
}
static int liblc3_encode(AVCodecContext *avctx, AVPacket *pkt,
const AVFrame *frame, int *got_packet_ptr)
{
LibLC3EncContext *liblc3 = avctx->priv_data;
int block_bytes = liblc3->block_bytes;
int channels = avctx->ch_layout.nb_channels;
void *zero_frame = NULL;
uint8_t *data_ptr;
int ret;
if ((ret = ff_get_encode_buffer(avctx, pkt, block_bytes, 0)) < 0)
return ret;
if (frame) {
int padding = frame->nb_samples - frame->duration;
liblc3->remaining_samples = FFMAX(liblc3->delay_samples - padding, 0);
} else {
if (!liblc3->remaining_samples)
return 0;
liblc3->remaining_samples = 0;
zero_frame = av_mallocz(avctx->frame_size * sizeof(float));
if (!zero_frame)
return AVERROR(ENOMEM);
}
data_ptr = pkt->data;
for (int ch = 0; ch < channels; ch++) {
const float *pcm = zero_frame ? zero_frame : frame->data[ch];
int nbytes = block_bytes / channels + (ch < block_bytes % channels);
lc3_encode(liblc3->encoder[ch],
LC3_PCM_FORMAT_FLOAT, pcm, 1, nbytes, data_ptr);
data_ptr += nbytes;
}
if (zero_frame)
av_free(zero_frame);
*got_packet_ptr = 1;
return 0;
}
#define OFFSET(x) offsetof(LibLC3EncContext, opts.x)
#define FLAGS AV_OPT_FLAG_AUDIO_PARAM | AV_OPT_FLAG_ENCODING_PARAM
static const AVOption options[] = {
{ "frame_duration", "Duration of a frame in milliseconds",
OFFSET(frame_duration), AV_OPT_TYPE_FLOAT,
{ .dbl = 10.0 }, 2.5, 10.0, FLAGS },
{ "high_resolution", "Enable High-Resolution mode (48 KHz or 96 KHz)",
OFFSET(hr_mode), AV_OPT_TYPE_BOOL,
{ .i64 = 0 }, 0, 1, FLAGS },
{ NULL }
};
static const AVClass class = {
.class_name = "liblc3 encoder",
.item_name = av_default_item_name,
.option = options,
.version = LIBAVUTIL_VERSION_INT,
};
const FFCodec ff_liblc3_encoder = {
.p.name = "liblc3",
CODEC_LONG_NAME("LC3 (Low Complexity Communication Codec)"),
.p.type = AVMEDIA_TYPE_AUDIO,
.p.id = AV_CODEC_ID_LC3,
.p.capabilities = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_DELAY,
.p.supported_samplerates = (const int [])
{ 96000, 48000, 32000, 24000, 16000, 8000, 0 },
.p.sample_fmts = (const enum AVSampleFormat[])
{ AV_SAMPLE_FMT_FLTP, AV_SAMPLE_FMT_NONE },
.p.priv_class = &class,
.p.wrapper_name = "liblc3",
.priv_data_size = sizeof(LibLC3EncContext),
.init = liblc3_encode_init,
.close = liblc3_encode_close,
FF_CODEC_ENCODE_CB(liblc3_encode),
};
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