基于ffmpeg的转码代码（转码为hls）

简介

本文基于ffmpeg api将视频转码为hls，其中可以设置hls_time，hls_list_size等参数。在此份代码中，也涉及了音视频转码的一些转码流程以及参数设置，供大家借鉴。

本份代码的运行环境为:ubuntu14.04。ffmpeg版本为2.6.1。大家也可改造一下，转码成不同的格式。

代码

hls.c

#include <stdio.h>#include <libavcodec/avcodec.h>#include <libavformat/avformat.h>#include <libavutil/opt.h>#include <libavutil/pixdesc.h>#include <libswresample/swresample.h>#include <libavutil/fifo.h>#include <libavfilter/avfiltergraph.h>#include <libavfilter/buffersink.h>#include <libavfilter/buffersrc.h>#include <libavutil/avutil.h>#define BUF_SIZE_20K 2048000#define BUF_SIZE_1K 1024000static AVFormatContext *ifmt_ctx;static AVFormatContext *ofmt_ctx;static SwrContext* pSwrCtx = NULL;AVBitStreamFilterContext* aacbsfc = NULL;void initSwr(int audio_index)  {      if (ofmt_ctx->streams[0]->codec->channels != ifmt_ctx->streams[audio_index]->codec->channels          || ofmt_ctx->streams[0]->codec->sample_rate != ifmt_ctx->streams[audio_index]->codec->sample_rate          || ofmt_ctx->streams[0]->codec->sample_fmt != ifmt_ctx->streams[audio_index]->codec->sample_fmt)      {          if ( NULL == pSwrCtx )           {              pSwrCtx = swr_alloc();          }  // #if LIBSWRESAMPLE_VERSION_MINOR >= 17    // 根据版本不同，选用适当函数          // av_opt_set_int(pSwrCtx, "ich", ifmt_ctx->streams[audio_index]->codec->channels, 0);          // av_opt_set_int(pSwrCtx, "och", ofmt_ctx->streams[audio_index]->codec->channels, 0);          // av_opt_set_int(pSwrCtx, "in_sample_rate",  ifmt_ctx->streams[audio_index]->codec->sample_rate, 0);          // av_opt_set_int(pSwrCtx, "out_sample_rate",  ofmt_ctx->streams[audio_index]->codec->sample_rate, 0);          // av_opt_set_sample_fmt(pSwrCtx, "in_sample_fmt", ifmt_ctx->streams[audio_index]->codec->sample_fmt, 0);          // av_opt_set_sample_fmt(pSwrCtx, "out_sample_fmt", ofmt_ctx->streams[audio_index]->codec->sample_fmt, 0);    // #else          pSwrCtx = swr_alloc_set_opts(NULL,                         ofmt_ctx->streams[audio_index]->codec->channel_layout,               ofmt_ctx->streams[audio_index]->codec->sample_fmt,               ofmt_ctx->streams[audio_index]->codec->sample_rate,              ifmt_ctx->streams[audio_index]->codec->channel_layout,               ifmt_ctx->streams[audio_index]->codec->sample_fmt,               ifmt_ctx->streams[audio_index]->codec->sample_rate,              0, NULL);  // #endif          swr_init(pSwrCtx);      }  }    //setup_array函数摘自ffmpeg例程  static void setup_array(uint8_t* out[32], AVFrame* in_frame, int format, int samples)  {      if (av_sample_fmt_is_planar(format))       {          int i;        int plane_size = av_get_bytes_per_sample((format & 0xFF)) * samples;        format &= 0xFF;                    //从decoder出来的frame中的data数据不是连续分布的，所以不能这样写：          in_frame->data[0]+i*plane_size;          for (i = 0; i < in_frame->channels; i++)          {              out[i] = in_frame->data[i];          }      }       else      {          out[0] = in_frame->data[0];      }  }int TransSample(AVFrame *in_frame, AVFrame *out_frame, int audio_index)  {      int ret;      int max_dst_nb_samples = 4096;      //int64_t dst_nb_samples;      int64_t src_nb_samples = in_frame->nb_samples;      out_frame->pts = in_frame->pts;      uint8_t* paudiobuf;      int decode_size, input_size, len;      if (pSwrCtx != NULL)       {          out_frame->nb_samples = av_rescale_rnd(swr_get_delay(pSwrCtx, ofmt_ctx->streams[audio_index]->codec->sample_rate) + src_nb_samples,              ofmt_ctx->streams[audio_index]->codec->sample_rate, ifmt_ctx->streams[audio_index]->codec->sample_rate, AV_ROUND_UP);            ret = av_samples_alloc(out_frame->data,               &out_frame->linesize[0],               ofmt_ctx->streams[audio_index]->codec->channels,               out_frame->nb_samples,               ofmt_ctx->streams[audio_index]->codec->sample_fmt, 0);                    if (ret < 0)          {              av_log(NULL, AV_LOG_WARNING, "[%s.%d %s() Could not allocate samples Buffer\n", __FILE__, __LINE__, __FUNCTION__);              return -1;          }                    max_dst_nb_samples = out_frame->nb_samples;          //输入也可能是分平面的，所以要做如下处理          uint8_t* m_ain[32];          setup_array(m_ain, in_frame, ifmt_ctx->streams[audio_index]->codec->sample_fmt, src_nb_samples);                    //注意这里，out_count和in_count是samples单位，不是byte          //所以这样av_get_bytes_per_sample(ifmt_ctx->streams[audio_index]->codec->sample_fmt) * src_nb_samples是错的          len = swr_convert(pSwrCtx, out_frame->data, out_frame->nb_samples, (const uint8_t**)in_frame->data, src_nb_samples);          if (len < 0)          {              char errmsg[BUF_SIZE_1K];              av_strerror(len, errmsg, sizeof(errmsg));              av_log(NULL, AV_LOG_WARNING, "[%s:%d] swr_convert!(%d)(%s)", __FILE__, __LINE__, len, errmsg);              return -1;          }      }      else      {          printf("pSwrCtx with out init!\n");          return -1;      }      return 0;  }  static int open_input_file(const char *filename){int ret;unsigned int i;ifmt_ctx = NULL;if ((ret = avformat_open_input(&ifmt_ctx, filename, NULL, NULL)) < 0) {av_log(NULL, AV_LOG_ERROR, "Cannot open input file\n");return ret;}if ((ret = avformat_find_stream_info(ifmt_ctx, NULL)) < 0) {av_log(NULL, AV_LOG_ERROR, "Cannot find stream information\n");return ret;}for (i = 0; i < ifmt_ctx->nb_streams; i++) {AVStream *stream;AVCodecContext *codec_ctx;stream = ifmt_ctx->streams[i];codec_ctx = stream->codec;/* Reencode video & audio and remux subtitles etc. */if (codec_ctx->codec_type == AVMEDIA_TYPE_VIDEO|| codec_ctx->codec_type == AVMEDIA_TYPE_AUDIO) {/* Open decoder */ret = avcodec_open2(codec_ctx,avcodec_find_decoder(codec_ctx->codec_id), NULL);if (ret < 0) {av_log(NULL, AV_LOG_ERROR, "Failed to open decoder for stream #%u\n", i);return ret;}}}av_dump_format(ifmt_ctx, 0, filename, 0);return 0;}static int open_output_file(const char *filename){AVStream *out_stream;AVStream *in_stream;AVCodecContext *dec_ctx, *enc_ctx;AVCodec *encoder;int ret;unsigned int i;ofmt_ctx = NULL;avformat_alloc_output_context2(&ofmt_ctx, NULL, "hls", filename);if (!ofmt_ctx) {av_log(NULL, AV_LOG_ERROR, "Could not create output context\n");return AVERROR_UNKNOWN;}for (i = 0; i < ifmt_ctx->nb_streams; i++) {out_stream = avformat_new_stream(ofmt_ctx, NULL);if (!out_stream) {av_log(NULL, AV_LOG_ERROR, "Failed allocating output stream\n");return AVERROR_UNKNOWN;}in_stream = ifmt_ctx->streams[i];dec_ctx = in_stream->codec;enc_ctx = out_stream->codec;if (dec_ctx->codec_type == AVMEDIA_TYPE_VIDEO) {encoder = avcodec_find_encoder(AV_CODEC_ID_H264);if (!encoder) {av_log(NULL, AV_LOG_FATAL, "Neccessary encoder not found\n");return AVERROR_INVALIDDATA;}enc_ctx->height = dec_ctx->height;enc_ctx->width = dec_ctx->width;enc_ctx->sample_aspect_ratio = dec_ctx->sample_aspect_ratio;enc_ctx->pix_fmt = encoder->pix_fmts[0];enc_ctx->time_base = dec_ctx->time_base;// enc_ctx->me_range = 25;// enc_ctx->max_qdiff = 4;enc_ctx->qmin = 10;enc_ctx->qmax = 51;// enc_ctx->qcompress = 0.6;// enc_ctx->refs = 3;enc_ctx->max_b_frames = 3;enc_ctx->gop_size = 250;enc_ctx->bit_rate = 500000;            enc_ctx->time_base.num = dec_ctx->time_base.num;            enc_ctx->time_base.den = dec_ctx->time_base.den;ret = avcodec_open2(enc_ctx, encoder, NULL);if (ret < 0) {av_log(NULL, AV_LOG_ERROR, "Cannot open video encoder for stream #%u\n", i);return ret;}                        av_opt_set(ofmt_ctx->priv_data, "preset", "superfast", 0);            av_opt_set(ofmt_ctx->priv_data, "tune", "zerolatency", 0);            // av_opt_set_int(ofmt_ctx->priv_data, "hls_time", 5, AV_OPT_SEARCH_CHILDREN);            // av_opt_set_int(ofmt_ctx->priv_data, "hls_list_size", 10, AV_OPT_SEARCH_CHILDREN);}else if (dec_ctx->codec_type == AVMEDIA_TYPE_UNKNOWN) {av_log(NULL, AV_LOG_FATAL, "Elementary stream #%d is of unknown type, cannot proceed\n", i);return AVERROR_INVALIDDATA;}else if (dec_ctx->codec_type == AVMEDIA_TYPE_AUDIO){encoder = avcodec_find_encoder(AV_CODEC_ID_AAC);enc_ctx->sample_rate = dec_ctx->sample_rate;enc_ctx->channel_layout = dec_ctx->channel_layout;enc_ctx->channels = av_get_channel_layout_nb_channels(enc_ctx->channel_layout);enc_ctx->sample_fmt = encoder->sample_fmts[0];AVRational ar = { 1, enc_ctx->sample_rate };enc_ctx->time_base = ar;ret = avcodec_open2(enc_ctx, encoder, NULL);if (ret < 0) {av_log(NULL, AV_LOG_ERROR, "Cannot open video encoder for stream #%u\n", i);return ret;}}else {ret = avcodec_copy_context(ofmt_ctx->streams[i]->codec,ifmt_ctx->streams[i]->codec);if (ret < 0) {av_log(NULL, AV_LOG_ERROR, "Copying stream context failed\n");return ret;}}if (ofmt_ctx->oformat->flags & AVFMT_GLOBALHEADER)enc_ctx->flags |= CODEC_FLAG_GLOBAL_HEADER;}av_dump_format(ofmt_ctx, 0, filename, 1);    // if (!(ofmt_ctx->oformat->flags & AVFMT_NOFILE)) {ret = avio_open(&ofmt_ctx->pb, filename, AVIO_FLAG_WRITE);if (ret < 0) {av_log(NULL, AV_LOG_ERROR, "Could not open output file '%s'", filename);return ret;}// }/* init muxer, write output file header */ret = avformat_write_header(ofmt_ctx, NULL);if (ret < 0) {av_log(NULL, AV_LOG_ERROR, "Error occurred when opening output file\n");return ret;}return 0;}static int encode_write_frame(AVFrame *filt_frame, unsigned int stream_index, int *got_frame) {    static a_total_duration = 0;    static v_total_duration = 0;int ret;int got_frame_local;AVPacket enc_pkt;int(*enc_func)(AVCodecContext *, AVPacket *, const AVFrame *, int *) =(ifmt_ctx->streams[stream_index]->codec->codec_type ==AVMEDIA_TYPE_VIDEO) ? avcodec_encode_video2 : avcodec_encode_audio2;if (!got_frame)got_frame = &got_frame_local;av_log(NULL, AV_LOG_INFO, "Encoding frame\n");/* encode filtered frame */enc_pkt.data = NULL;enc_pkt.size = 0;av_init_packet(&enc_pkt);ret = enc_func(ofmt_ctx->streams[stream_index]->codec, &enc_pkt,filt_frame, got_frame);if (ret < 0)return ret;if (!(*got_frame))return 0;    // if (ifmt_ctx->streams[stream_index]->codec->codec_type !=// AVMEDIA_TYPE_VIDEO)        // av_bitstream_filter_filter(aacbsfc, ofmt_ctx->streams[stream_index]->codec, NULL, &enc_pkt.data, &enc_pkt.size, enc_pkt.data, enc_pkt.size, 0);    /* prepare packet for muxing */enc_pkt.stream_index = stream_index;av_packet_rescale_ts(&enc_pkt,ofmt_ctx->streams[stream_index]->codec->time_base,ofmt_ctx->streams[stream_index]->time_base);                if (ifmt_ctx->streams[stream_index]->codec->codec_type !=AVMEDIA_TYPE_VIDEO){        enc_pkt.pts = enc_pkt.dts = a_total_duration;        a_total_duration += av_rescale_q(filt_frame->nb_samples, ofmt_ctx->streams[stream_index]->codec->time_base, ofmt_ctx->streams[stream_index]->time_base);    }    // printf("v_total_duration: %d, a_total_duration: %d\n", v_total_duration, a_total_duration);av_log(NULL, AV_LOG_DEBUG, "Muxing frame\n");/* mux encoded frame */ret = av_interleaved_write_frame(ofmt_ctx, &enc_pkt);return ret;}static int flush_encoder(unsigned int stream_index){int ret;int got_frame;    AVPacket enc_pkt;if (!(ofmt_ctx->streams[stream_index]->codec->codec->capabilities &CODEC_CAP_DELAY))return 0;while (1) {        enc_pkt.data = NULL;        enc_pkt.size = 0;        av_init_packet(&enc_pkt);av_log(NULL, AV_LOG_INFO, "Flushing stream #%u encoder\n", stream_index);ret = encode_write_frame(NULL, stream_index, &got_frame);if (ret < 0)break;if (!got_frame)return 0;}return ret;}int main(int argc, char **argv){int ret;AVPacket packet; //= { .data = NULL, .size = 0 };packet.data = NULL;packet.size = 0;AVFrame *frame = NULL;enum AVMediaType type;unsigned int stream_index;unsigned int i;int got_frame;int(*dec_func)(AVCodecContext *, AVFrame *, int *, const AVPacket *);av_register_all();avfilter_register_all();if ((ret = open_input_file("test.flv")) < 0)goto end;if ((ret = open_output_file("test.m3u8")) < 0)goto end;    aacbsfc = av_bitstream_filter_init("aac_adtstoasc");/* read all packets */    int count = 0;    int flag = 1;while (1) {if ((ret = av_read_frame(ifmt_ctx, &packet)) < 0)break;stream_index = packet.stream_index;type = ifmt_ctx->streams[packet.stream_index]->codec->codec_type;av_log(NULL, AV_LOG_DEBUG, "Demuxer gave frame of stream_index %u\n",stream_index);        av_log(NULL, AV_LOG_DEBUG, "Going to reencode&filter the frame\n");        frame = av_frame_alloc();        if (!frame) {            ret = AVERROR(ENOMEM);            break;        }        av_packet_rescale_ts(&packet,            ifmt_ctx->streams[stream_index]->time_base,            ifmt_ctx->streams[stream_index]->codec->time_base);        dec_func = (type == AVMEDIA_TYPE_VIDEO) ? avcodec_decode_video2 :            avcodec_decode_audio4;        ret = dec_func(ifmt_ctx->streams[stream_index]->codec, frame,            &got_frame, &packet);        if (ret < 0) {            av_frame_free(&frame);            av_log(NULL, AV_LOG_ERROR, "Decoding failed\n");            break;        }        if (got_frame) {            frame->pts = frame->pkt_pts;            // frame->pts = av_frame_get_best_effort_timestamp(frame);            // frame->pts=count;            if (type == AVMEDIA_TYPE_VIDEO){                ret = encode_write_frame(frame, stream_index, NULL);            }else {                if (flag){                    initSwr(stream_index);                    flag = 0;                }                                    AVFrame *frame_out = av_frame_alloc();                if (0 != TransSample(frame, frame_out, stream_index)){                    av_log(NULL, AV_LOG_ERROR, "convert audio failed\n");                    ret = -1;                }                // frame_out->pts = frame->pkt_pts;                ret = encode_write_frame(frame_out, stream_index, NULL);                av_frame_free(&frame_out);            }            av_frame_free(&frame);            if (ret < 0)                goto end;        }        else {            av_frame_free(&frame);        }av_free_packet(&packet);        ++count;}    /* flush  encoders */// for (i = 0; i < ifmt_ctx->nb_streams; i++) {// ret = flush_encoder(i);// if (ret < 0) {// av_log(NULL, AV_LOG_ERROR, "Flushing encoder failed\n");// goto end;// }// }    av_log(NULL, AV_LOG_ERROR, "Flushing encoder failed\n");av_write_trailer(ofmt_ctx);end:av_free_packet(&packet);av_frame_free(&frame);    av_bitstream_filter_close(aacbsfc);for (i = 0; i < ifmt_ctx->nb_streams; i++) {avcodec_close(ifmt_ctx->streams[i]->codec);if (ofmt_ctx && ofmt_ctx->nb_streams > i && ofmt_ctx->streams[i] && ofmt_ctx->streams[i]->codec)avcodec_close(ofmt_ctx->streams[i]->codec);}// av_free(filter_ctx);avformat_close_input(&ifmt_ctx);if (ofmt_ctx && !(ofmt_ctx->oformat->flags & AVFMT_NOFILE))avio_closep(&ofmt_ctx->pb);avformat_free_context(ofmt_ctx);// if (ret < 0)// av_log(NULL, AV_LOG_ERROR, "Error occurred: %s\n", av_err2str(ret)); //av_err2str(ret));return ret ? 1 : 0;}

编译

编译命令：

       gcc hls.c -g -o hls -lavformat -lavutil -lavcodec -lswscale

重点片段

1.视频帧率最好设置成与原视频一样，否则会有音视频不同步的现象

2.音频转码需要用swr转换一下sample。否则音频转码出来是噪音

3.转码为hls不需要用aacbsfc，但是我把output的格式换成flv后，需要用aacbsfc才能正常转码音频

代码下载

除了本份代码，我还基于ffmpeg自带的转码例子改造了一份转码hls的代码。一起提交到cdsn供大家下载。（ffmpeg自带的例子用的是filter，省了自己设置各种参数和格式转换）

http://download.csdn.net/detail/yingyemin/9918532

http://download.csdn.net/detail/yingyemin/9918545