/*
 * Copyright (c) 2023 Fancy Code.
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
#include "FfmpegMuxStream.h"
#include "ILog.h"
#include "MediaBase.h"
#include "StatusCode.h"
#include <cstddef>
#include <cstdlib>
#include <stdio.h>
#include <string.h>
#include <string>
#ifdef __cplusplus
extern "C" {
#endif
#include <libavcodec/avcodec.h>
#include <libavcodec/codec.h>
#include <libavcodec/codec_id.h>
#include <libavcodec/packet.h>
#include <libavformat/avformat.h>
#include <libavformat/avio.h>
#include <libavutil/avutil.h>
#include <libavutil/channel_layout.h>
#include <libavutil/dict.h>
#include <libavutil/error.h>
#include <libavutil/frame.h>
#include <libavutil/opt.h>
#include <libavutil/pixfmt.h>
#include <libavutil/samplefmt.h>
#include <libavutil/timestamp.h>
#include <libswresample/swresample.h>
#include <libswscale/swscale.h>
#ifdef __cplusplus
}
#endif
#include <errno.h>
#include <math.h>
#define STREAM_DURATION 10.0
#define STREAM_FRAME_RATE 25              /* 25 images/s */
#define STREAM_PIX_FMT AV_PIX_FMT_YUV420P /* default pix_fmt */
FfmpegMuxStream::FfmpegMuxStream()
    : mCodecVideo(nullptr), mCodecVideoContext(nullptr), mFrameVideo(nullptr), mCodecAudio(nullptr),
      mCodecAudioContext(nullptr), mFrameAudio(nullptr), mOc(nullptr)
{
    memset(&mVideoSt, 0, sizeof(mVideoSt));
    memset(&mAudioSt, 0, sizeof(mAudioSt));
}
StatusCode FfmpegMuxStream::OpenOutputFile(const std::string &fileName)
{
    if (!InitCodecVideo(AV_CODEC_ID_H264, &mCodecVideo, &mCodecVideoContext, &mFrameVideo)) {
        LogError("InitCodec failed\n");
        return CreateStatusCode(STATUS_CODE_NOT_OK);
    }
    if (!InitCodecAudio(AV_CODEC_ID_PCM_ALAW, &mCodecAudio, &mCodecAudioContext, &mFrameAudio)) {
        LogError("InitCodec failed\n");
        return CreateStatusCode(STATUS_CODE_NOT_OK);
    }
    int ret;
    AVFormatContext *oc = nullptr;
    int have_video = 0, have_audio = 0;
    int encode_video = 0, encode_audio = 0;
    const AVCodec *audio_codec, *video_codec;
    AVDictionary *opt = nullptr;
    avformat_alloc_output_context2(&oc, nullptr, "mp4", fileName.c_str());
    if (!oc) {
        LogError("Could not deduce output format from file extension: using MPEG.\n");
        return CreateStatusCode(STATUS_CODE_NOT_OK);
    }
    mOc = oc;
    const AVOutputFormat *fmt = oc->oformat;
    /* Add the audio and video streams using the default format codecs
     * and initialize the codecs. */
    if (fmt->video_codec != AV_CODEC_ID_NONE) {
        LogInfo("Add video stream\n");
        add_stream(&mVideoSt, oc, &video_codec, fmt->video_codec);
        have_video = 1;
        encode_video = 1;
    }
    if (fmt->audio_codec != AV_CODEC_ID_NONE) {
        LogInfo("Add audio stream\n");
        add_stream(&mAudioSt, oc, &audio_codec, fmt->audio_codec);
        have_audio = 1;
        encode_audio = 1;
    } /* Now that all the parameters are set, we can open the audio and
       * video codecs and allocate the necessary encode buffers. */
    if (have_video) {
        open_video(oc, video_codec, &mVideoSt, opt);
    }

    if (have_audio) {
        open_audio(oc, audio_codec, &mAudioSt, opt);
    }
    av_dump_format(oc, 0, fileName.c_str(), 1);
    if (!(fmt->flags & AVFMT_NOFILE)) {
        ret = avio_open(&oc->pb, fileName.c_str(), AVIO_FLAG_WRITE);
        if (ret < 0) {
            char error_str[AV_ERROR_MAX_STRING_SIZE] = {0};
            LogInfo("Could not open '%s': %s\n",
                    fileName.c_str(),
                    av_make_error_string(error_str, AV_ERROR_MAX_STRING_SIZE, ret));
            return CreateStatusCode(STATUS_CODE_NOT_OK);
        }
    }
    /* Write the stream header, if any. */
    ret = avformat_write_header(oc, &opt);
    if (ret < 0) {
        char error_str[AV_ERROR_MAX_STRING_SIZE] = {0};
        LogInfo("Error occurred when opening output file: %s\n",
                av_make_error_string(error_str, AV_ERROR_MAX_STRING_SIZE, ret));
        return CreateStatusCode(STATUS_CODE_NOT_OK);
    }
    return CreateStatusCode(STATUS_CODE_OK);
}
StatusCode FfmpegMuxStream::CloseOutputFile(void)
{
    av_write_trailer(mOc);
    if (mFrameVideo) {
        av_frame_free(&mFrameVideo);
        mFrameVideo = nullptr;
    }
    if (mFrameAudio) {
        av_frame_free(&mFrameAudio);
        mFrameAudio = nullptr;
    }
    if (mCodecVideoContext) {
        avcodec_free_context(&mCodecVideoContext);
        mCodecVideoContext = nullptr;
    }
    if (mCodecAudioContext) {
        avcodec_free_context(&mCodecAudioContext);
        mCodecAudioContext = nullptr;
    }
    close_stream(mOc, &mVideoSt);
    close_stream(mOc, &mAudioSt);
    memset(&mVideoSt, 0, sizeof(mVideoSt));
    memset(&mAudioSt, 0, sizeof(mAudioSt));
    if (!(mOc->oformat->flags & AVFMT_NOFILE)) {
        /* Close the output file. */
        avio_closep(&mOc->pb);
    }
    avformat_free_context(mOc);
    return CreateStatusCode(STATUS_CODE_OK);
}
void FfmpegMuxStream::GetStreamData(const void *data, const size_t &size, const StreamInfo &streamInfo)
{
    if (streamInfo.mType == STREAM_TYPE_VIDEO_H264) {
        GetVideoStream(data, size, streamInfo);
    }
    if (streamInfo.mType == STREAM_TYPE_AUDIO_G711A) {
        GetAudioStream(data, size, streamInfo);
    }
}
void FfmpegMuxStream::GetVideoStream(const void *data, const size_t &size, const StreamInfo &streamInfo)
{
    AVPacket *packet = nullptr;
    packet = av_packet_alloc();
    packet->data = (unsigned char *)data;
    packet->size = size;
    int ret = avcodec_send_packet(mCodecVideoContext, packet);
    if (ret < 0) {
        LogInfo("Error sending a packet for decoding\n");
        av_packet_unref(packet);
        av_packet_free(&packet);
        return;
    }
    while (ret >= 0) {
        ret = avcodec_receive_frame(mCodecVideoContext, mFrameVideo);
        if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
            break;
        }
        if (ret < 0) {
            LogInfo("Error during decoding\n");
            break;
        }
        write_frame(mOc, mVideoSt.enc, mVideoSt.st, mFrameVideo, mVideoSt.tmp_pkt);
        break;
    }
    av_packet_unref(packet);
    av_packet_free(&packet);
}
void FfmpegMuxStream::GetAudioStream(const void *data, const size_t &size, const StreamInfo &streamInfo)
{
    AVPacket *packet = nullptr;
    packet = av_packet_alloc();
    packet->data = (unsigned char *)data;
    packet->size = size;
    int ret = avcodec_send_packet(mCodecAudioContext, packet);
    if (ret < 0) {
        LogInfo("Error sending a packet for decoding\n");
        av_packet_unref(packet);
        av_packet_free(&packet);
        return;
    }
    while (ret >= 0) {
        ret = avcodec_receive_frame(mCodecAudioContext, mFrameAudio);
        if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
            break;
        }
        if (ret < 0) {
            LogInfo("Error during decoding\n");
            break;
        }
        mFrameAudio->pts = mAudioSt.next_pts;
        mAudioSt.next_pts += mFrameAudio->nb_samples;
        ConvertAudioFrame(mFrameVideo, mAudioSt.enc, &mAudioSt);
        write_frame(mOc, mAudioSt.enc, mAudioSt.st, mAudioSt.frame, mAudioSt.tmp_pkt);
        break;
    }
    av_packet_unref(packet);
    av_packet_free(&packet);
}
bool FfmpegMuxStream::add_stream(OutputStream *ost, AVFormatContext *oc, const AVCodec **codec, enum AVCodecID codec_id)
{
    AVCodecContext *c;
    int i;

    /* find the encoder */
    *codec = avcodec_find_encoder(codec_id);
    if (!(*codec)) {
        LogError("Could not find encoder for '%s'\n", avcodec_get_name(codec_id));
        return false;
    }

    ost->tmp_pkt = av_packet_alloc();
    if (!ost->tmp_pkt) {
        LogError("Could not allocate AVPacket\n");
        return false;
    }

    ost->st = avformat_new_stream(oc, nullptr);
    if (!ost->st) {
        LogError("Could not allocate stream\n");
        return false;
    }
    ost->st->id = oc->nb_streams - 1;
    c = avcodec_alloc_context3(*codec);
    if (!c) {
        LogError("Could not alloc an encoding context\n");
        return false;
    }
    ost->enc = c;

    const AVChannelLayout src = (AVChannelLayout)AV_CHANNEL_LAYOUT_STEREO;
    switch ((*codec)->type) {
    case AVMEDIA_TYPE_AUDIO:
        c->sample_fmt = (*codec)->sample_fmts ? (*codec)->sample_fmts[0] : AV_SAMPLE_FMT_FLTP;
        c->bit_rate = 64000;
        c->sample_rate = 8000;
        if ((*codec)->supported_samplerates) {
            c->sample_rate = (*codec)->supported_samplerates[0];
            for (i = 0; (*codec)->supported_samplerates[i]; i++) {
                if ((*codec)->supported_samplerates[i] == 44100)
                    c->sample_rate = 44100;
            }
        }
        av_channel_layout_copy(&c->ch_layout, &src);
        ost->st->time_base = (AVRational){1, c->sample_rate};
        break;

    case AVMEDIA_TYPE_VIDEO:
        c->codec_id = codec_id;

        c->bit_rate = 400000;
        /* Resolution must be a multiple of two. */
        c->width = 1920;
        c->height = 2160;
        /* timebase: This is the fundamental unit of time (in seconds) in terms
         * of which frame timestamps are represented. For fixed-fps content,
         * timebase should be 1/framerate and timestamp increments should be
         * identical to 1. */
        ost->st->time_base = (AVRational){1, STREAM_FRAME_RATE};
        c->time_base = ost->st->time_base;

        c->gop_size = 12; /* emit one intra frame every twelve frames at most */
        c->pix_fmt = STREAM_PIX_FMT;
        if (c->codec_id == AV_CODEC_ID_MPEG2VIDEO) {
            /* just for testing, we also add B-frames */
            c->max_b_frames = 2;
        }
        if (c->codec_id == AV_CODEC_ID_MPEG1VIDEO) {
            /* Needed to avoid using macroblocks in which some coeffs overflow.
             * This does not happen with normal video, it just happens here as
             * the motion of the chroma plane does not match the luma plane. */
            c->mb_decision = 2;
        }
        break;

    default:
        break;
    }

    /* Some formats want stream headers to be separate. */
    if (oc->oformat->flags & AVFMT_GLOBALHEADER) {
        c->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
    }
    return true;
}
void FfmpegMuxStream::close_stream(AVFormatContext *oc, OutputStream *ost)
{
    avcodec_free_context(&ost->enc);
    av_frame_free(&ost->frame);
    av_frame_free(&ost->tmp_frame);
    av_packet_free(&ost->tmp_pkt);
    sws_freeContext(ost->sws_ctx);
    swr_free(&ost->swr_ctx);
}
bool FfmpegMuxStream::open_video(AVFormatContext *oc, const AVCodec *codec, OutputStream *ost, AVDictionary *opt_arg)
{

    int ret;
    AVCodecContext *c = ost->enc;
    AVDictionary *opt = nullptr;

    av_dict_copy(&opt, opt_arg, 0);

    /* open the codec */
    ret = avcodec_open2(c, codec, &opt);
    av_dict_free(&opt);
    if (ret < 0) {
        char error_str[AV_ERROR_MAX_STRING_SIZE] = {0};
        LogInfo("Could not open video codec: %s\n", av_make_error_string(error_str, AV_ERROR_MAX_STRING_SIZE, ret));
        return false;
    }

    /* allocate and init a re-usable frame */
    ost->frame = alloc_frame(c->pix_fmt, c->width, c->height);
    if (!ost->frame) {
        LogInfo("Could not allocate video frame\n");
        return false;
    }

    /* If the output format is not YUV420P, then a temporary YUV420P
     * picture is needed too. It is then converted to the required
     * output format. */
    ost->tmp_frame = nullptr;
    if (c->pix_fmt != AV_PIX_FMT_YUV420P) {
        ost->tmp_frame = alloc_frame(AV_PIX_FMT_YUV420P, c->width, c->height);
        if (!ost->tmp_frame) {
            LogInfo("Could not allocate temporary video frame\n");
            return false;
        }
    }

    /* copy the stream parameters to the muxer */
    ret = avcodec_parameters_from_context(ost->st->codecpar, c);
    if (ret < 0) {
        LogInfo("Could not copy the stream parameters\n");
        return false;
    }
    return true;
}
bool FfmpegMuxStream::open_audio(AVFormatContext *oc, const AVCodec *codec, OutputStream *ost, AVDictionary *opt_arg)
{
    AVCodecContext *c = nullptr;
    int nb_samples = 0;
    int ret = 0;
    AVDictionary *opt = nullptr;

    c = ost->enc;

    /* open it */
    av_dict_copy(&opt, opt_arg, 0);
    ret = avcodec_open2(c, codec, &opt);
    av_dict_free(&opt);
    if (ret < 0) {
        char error_str[AV_ERROR_MAX_STRING_SIZE] = {0};
        LogInfo("Could not open audio codec: %s\n", av_make_error_string(error_str, AV_ERROR_MAX_STRING_SIZE, ret));
        return false;
    }

    /* init signal generator */
    ost->t = 0;
    ost->tincr = 2 * M_PI * 110.0 / c->sample_rate;
    /* increment frequency by 110 Hz per second */
    ost->tincr2 = 2 * M_PI * 110.0 / c->sample_rate / c->sample_rate;

    if (c->codec->capabilities & AV_CODEC_CAP_VARIABLE_FRAME_SIZE)
        nb_samples = 10000;
    else
        nb_samples = c->frame_size;

    ost->frame = alloc_audio_frame(c->sample_fmt, &c->ch_layout, c->sample_rate, nb_samples);
    ost->tmp_frame = alloc_audio_frame(AV_SAMPLE_FMT_S16, &c->ch_layout, c->sample_rate, nb_samples);

    /* copy the stream parameters to the muxer */
    ret = avcodec_parameters_from_context(ost->st->codecpar, c);
    if (ret < 0) {
        LogInfo("Could not copy the stream parameters\n");
        return false;
    }

    /* create resampler context */
    ost->swr_ctx = swr_alloc();
    if (!ost->swr_ctx) {
        LogInfo("Could not allocate resampler context\n");
        return false;
    }

    /* set options */
    av_opt_set_chlayout(ost->swr_ctx, "in_chlayout", &c->ch_layout, 0);
    av_opt_set_int(ost->swr_ctx, "in_sample_rate", c->sample_rate, 0);
    av_opt_set_sample_fmt(ost->swr_ctx, "in_sample_fmt", AV_SAMPLE_FMT_S16, 0);
    av_opt_set_chlayout(ost->swr_ctx, "out_chlayout", &c->ch_layout, 0);
    av_opt_set_int(ost->swr_ctx, "out_sample_rate", c->sample_rate, 0);
    av_opt_set_sample_fmt(ost->swr_ctx, "out_sample_fmt", c->sample_fmt, 0);

    /* initialize the resampling context */
    if ((ret = swr_init(ost->swr_ctx)) < 0) {
        LogInfo("Failed to initialize the resampling context\n");
        return false;
    }
    return true;
}
AVFrame *FfmpegMuxStream::alloc_audio_frame(enum AVSampleFormat sample_fmt, const AVChannelLayout *channel_layout,
                                            int sample_rate, int nb_samples)
{
    AVFrame *frame = av_frame_alloc();
    if (!frame) {
        LogInfo("Error allocating an audio frame\n");
        return nullptr;
    }

    frame->format = sample_fmt;
    av_channel_layout_copy(&frame->ch_layout, channel_layout);
    frame->sample_rate = sample_rate;
    frame->nb_samples = nb_samples;

    if (nb_samples) {
        if (av_frame_get_buffer(frame, 0) < 0) {
            LogInfo("Error allocating an audio buffer\n");
            return nullptr;
        }
    }

    return frame;
}
AVFrame *FfmpegMuxStream::alloc_frame(enum AVPixelFormat pix_fmt, int width, int height)
{
    AVFrame *frame;
    int ret;

    frame = av_frame_alloc();
    if (!frame)
        return nullptr;

    frame->format = pix_fmt;
    frame->width = width;
    frame->height = height;

    /* allocate the buffers for the frame data */
    ret = av_frame_get_buffer(frame, 0);
    if (ret < 0) {
        LogInfo("Could not allocate frame data.\n");
        return nullptr;
    }

    return frame;
}
bool FfmpegMuxStream::InitCodecVideo(enum AVCodecID codecId, AVCodec **codec, AVCodecContext **codec_ctx,
                                     AVFrame **frame)
{
    int ret = 0;
    *codec = (AVCodec *)avcodec_find_decoder(codecId);
    if (!(*codec)) {
        LogError("Codec not found\n");
        return false;
    }
    *codec_ctx = avcodec_alloc_context3((const AVCodec *)(*codec));
    if (!(*codec_ctx)) {
        LogError("Could not allocate codec context\n");
        return false;
    }
    if ((ret = avcodec_open2(*codec_ctx, *codec, nullptr)) < 0) {
        char error_str[AV_ERROR_MAX_STRING_SIZE] = {0};
        LogError("Could not open codec:%s\n", av_make_error_string(error_str, AV_ERROR_MAX_STRING_SIZE, ret));
        return false;
    }
    *frame = av_frame_alloc();
    if (!frame) {
        LogError("Could not allocate video frame\n");
        return false;
    }
    return true;
}
bool FfmpegMuxStream::InitCodecAudio(enum AVCodecID codecId, AVCodec **codec, AVCodecContext **codec_ctx,
                                     AVFrame **frame)
{
    int ret = 0;
    *codec = (AVCodec *)avcodec_find_decoder(codecId);
    // *codec = (AVCodec *)avcodec_find_encoder_by_name("libfdk_aac");
    if (!(*codec)) {
        LogError("Codec not found\n");
        return false;
    }
    *codec_ctx = avcodec_alloc_context3((const AVCodec *)(*codec));
    if (!(*codec_ctx)) {
        LogError("Could not allocate codec context\n");
        return false;
    }
    /* put sample parameters */
    (*codec_ctx)->bit_rate = 64000;

    /* check that the encoder supports s16 pcm input */
    (*codec_ctx)->sample_fmt = AV_SAMPLE_FMT_S16;
    if (!check_sample_fmt((*codec), (*codec_ctx)->sample_fmt)) {
        fprintf(stderr, "Encoder does not support sample format %s", av_get_sample_fmt_name((*codec_ctx)->sample_fmt));
        return false;
    }

    /* select other audio parameters supported by the encoder */
    (*codec_ctx)->sample_rate = select_sample_rate((*codec));
    ret = select_channel_layout((*codec), &((*codec_ctx)->ch_layout));
    if (ret < 0) {
        LogError("Could not set channel layout\n");
        return false;
    }
    if ((ret = avcodec_open2(*codec_ctx, *codec, nullptr)) < 0) {
        char error_str[AV_ERROR_MAX_STRING_SIZE] = {0};
        LogError("Could not open codec:%s\n", av_make_error_string(error_str, AV_ERROR_MAX_STRING_SIZE, ret));
        return false;
    }
    *frame = av_frame_alloc();
    if (!(*frame)) {
        LogError("Could not allocate video frame\n");
        return false;
    }
    (*frame)->nb_samples = (*codec_ctx)->frame_size;
    (*frame)->format = (*codec_ctx)->sample_fmt;
    ret = av_channel_layout_copy(&((*frame)->ch_layout), &((*codec_ctx)->ch_layout));
    if (ret < 0) {
        LogError("Could not copy channel layout\n");
        return false;
    }
    return true;
}
int FfmpegMuxStream::write_frame(AVFormatContext *fmt_ctx, AVCodecContext *c, AVStream *st, AVFrame *frame,
                                 AVPacket *pkt)
{
    int ret = 0;
    // send the frame to the encoder
    ret = avcodec_send_frame(c, frame);
    if (ret < 0) {
        char error_str[AV_ERROR_MAX_STRING_SIZE] = {0};
        LogInfo("Error sending a frame to the encoder: %s\n",
                av_make_error_string(error_str, AV_ERROR_MAX_STRING_SIZE, ret));
        return -1;
    }

    while (ret >= 0) {
        ret = avcodec_receive_packet(c, pkt);
        if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
            break;
        }
        if (ret < 0) {
            char error_str[AV_ERROR_MAX_STRING_SIZE] = {0};
            LogInfo("Error encoding a frame: %s\n", av_make_error_string(error_str, AV_ERROR_MAX_STRING_SIZE, ret));
            return -1;
        }

        /* rescale output packet timestamp values from codec to stream timebase */
        av_packet_rescale_ts(pkt, c->time_base, st->time_base);
        pkt->stream_index = st->index;

        /* Write the compressed frame to the media file. */
        log_packet(fmt_ctx, pkt);
        ret = av_interleaved_write_frame(fmt_ctx, pkt);
        /* pkt is now blank (av_interleaved_write_frame() takes ownership of
         * its contents and resets pkt), so that no unreferencing is necessary.
         * This would be different if one used av_write_frame(). */
        if (ret < 0) {
            char error_str[AV_ERROR_MAX_STRING_SIZE] = {0};
            LogInfo("Error while writing output packet: %s\n",
                    av_make_error_string(error_str, AV_ERROR_MAX_STRING_SIZE, ret));
            return -1;
        }
    }

    return ret == AVERROR_EOF ? 1 : 0;
}
void FfmpegMuxStream::log_packet(const AVFormatContext *fmt_ctx, const AVPacket *pkt)
{
    char pts[AV_TS_MAX_STRING_SIZE] = {0};
    char dts[AV_TS_MAX_STRING_SIZE] = {0};
    char duration[AV_TS_MAX_STRING_SIZE] = {0};
    char pts_time[AV_TS_MAX_STRING_SIZE] = {0};
    char dts_time[AV_TS_MAX_STRING_SIZE] = {0};
    char duration_time[AV_TS_MAX_STRING_SIZE];
    AVRational *time_base = &fmt_ctx->streams[pkt->stream_index]->time_base;
    av_ts_make_string(pts, pkt->pts);
    LogInfo("pts:%s pts_time:%s dts:%s dts_time:%s duration:%s duration_time:%s stream_index:%d\n",
            av_ts_make_string(pts, pkt->pts),
            av_ts_make_time_string(pts_time, pkt->pts, time_base),
            av_ts_make_string(dts, pkt->dts),
            av_ts_make_time_string(dts_time, pkt->dts, time_base),
            av_ts_make_string(duration, pkt->duration),
            av_ts_make_time_string(duration_time, pkt->duration, time_base),
            pkt->stream_index);
}
/* check that a given sample format is supported by the encoder */
int FfmpegMuxStream::check_sample_fmt(const AVCodec *codec, enum AVSampleFormat sample_fmt)
{
    const enum AVSampleFormat *p = codec->sample_fmts;

    while (*p != AV_SAMPLE_FMT_NONE) {
        if (*p == sample_fmt)
            return 1;
        p++;
    }
    return 0;
}
/* just pick the highest supported samplerate */
int FfmpegMuxStream::select_sample_rate(const AVCodec *codec)
{
    const int *p;
    int best_samplerate = 0;

    if (!codec->supported_samplerates)
        return 44100;

    p = codec->supported_samplerates;
    while (*p) {
        if (!best_samplerate || abs(44100 - *p) < abs(44100 - best_samplerate))
            best_samplerate = *p;
        p++;
    }
    return best_samplerate;
} /* select layout with the highest channel count */
int FfmpegMuxStream::select_channel_layout(const AVCodec *codec, AVChannelLayout *dst)
{
    const AVChannelLayout *p, *best_ch_layout = nullptr;
    int best_nb_channels = 0;
    AVChannelLayout channelLayout = AV_CHANNEL_LAYOUT_STEREO;
    if (!codec->ch_layouts)
        return av_channel_layout_copy(dst, &channelLayout);

    p = codec->ch_layouts;
    while (p->nb_channels) {
        int nb_channels = p->nb_channels;

        if (nb_channels > best_nb_channels) {
            best_ch_layout = p;
            best_nb_channels = nb_channels;
        }
        p++;
    }
    return av_channel_layout_copy(dst, best_ch_layout);
}
bool FfmpegMuxStream::ConvertAudioFrame(AVFrame *frame, AVCodecContext *c, OutputStream *ost)
{
    if (nullptr == frame) {
        LogError("frame is null\n");
        return false;
    }
    int ret = 0;
    int dst_nb_samples = 0;
    /* convert samples from native format to destination codec format, using the resampler */
    /* compute destination number of samples */
    dst_nb_samples = av_rescale_rnd(
        swr_get_delay(ost->swr_ctx, c->sample_rate) + frame->nb_samples, c->sample_rate, c->sample_rate, AV_ROUND_UP);
    av_assert0(dst_nb_samples == frame->nb_samples);

    /* when we pass a frame to the encoder, it may keep a reference to it
     * internally;
     * make sure we do not overwrite it here
     */
    ret = av_frame_make_writable(ost->frame);
    if (ret < 0) {
        LogError("av_frame_make_writable failed\n");
        return false;
    }

    /* convert to destination format */
    ret = swr_convert(ost->swr_ctx, ost->frame->data, dst_nb_samples, (const uint8_t **)frame->data, frame->nb_samples);
    if (ret < 0) {
        LogError("Error while converting\n");
        return false;
    }
    frame = ost->frame;

    frame->pts = av_rescale_q(ost->samples_count, (AVRational){1, c->sample_rate}, c->time_base);
    ost->samples_count += dst_nb_samples;
    return true;
}