利用FFmpeg将mkv视频转换为H.264

本文介绍一个简单的基于FFmpeg的转码器，其将MKV文件转换为mp4g格式，采用H.264编码，主要是为了学习并记录相应的流程。

现贴上代码：

const char* SRC_FILE = "Titanic.mkv";const char* OUT_FILE = "Titanic.h264";const char* OUT_FMT_FILE = "Titanic.mp4";int _tmain(int argc, _TCHAR* argv[]){av_register_all();AVFormatContext* pFormat = NULL;if (avformat_open_input(&pFormat, SRC_FILE, NULL, NULL) < 0){return 0;}AVCodecContext* video_dec_ctx = NULL;AVCodec* video_dec = NULL;if (avformat_find_stream_info(pFormat, NULL) < 0){return 0;}av_dump_format(pFormat, 0, SRC_FILE, 0);video_dec_ctx = pFormat->streams[0]->codec;video_dec = avcodec_find_decoder(video_dec_ctx->codec_id);if (avcodec_open2(video_dec_ctx, video_dec, NULL) < 0){return 0;}AVFormatContext* pOFormat = NULL;AVOutputFormat* ofmt = NULL;if (avformat_alloc_output_context2(&pOFormat, NULL, NULL, OUT_FILE) < 0){return 0;}ofmt = pOFormat->oformat;if (avio_open(&(pOFormat->pb), OUT_FILE, AVIO_FLAG_READ_WRITE) < 0){return 0;}AVCodecContext *video_enc_ctx = NULL;AVCodec *video_enc = NULL;video_enc = avcodec_find_encoder(AV_CODEC_ID_H264);AVStream *video_st = avformat_new_stream(pOFormat, video_enc);if (!video_st)return 0;video_enc_ctx = video_st->codec;video_enc_ctx->width = video_dec_ctx->width;video_enc_ctx->height = video_dec_ctx->height;video_enc_ctx->pix_fmt = AV_PIX_FMT_YUV420P;video_enc_ctx->time_base.num = 1;video_enc_ctx->time_base.den = 25;video_enc_ctx->bit_rate = video_dec_ctx->bit_rate;video_enc_ctx->gop_size = 250;video_enc_ctx->max_b_frames = 10;video_enc_ctx->qmin = 10;video_enc_ctx->qmax = 51;if (avcodec_open2(video_enc_ctx, video_enc, NULL) < 0){printf("编码器打开失败！\n");return 0;}printf("Output264video Information====================\n");av_dump_format(pOFormat, 0, OUT_FILE, 1);printf("Output264video Information====================\n");//mp4 fileAVFormatContext* pMp4Format = NULL;AVOutputFormat* pMp4OFormat = NULL;if (avformat_alloc_output_context2(&pMp4Format, NULL, NULL, OUT_FMT_FILE) < 0){return 0;}pMp4OFormat = pMp4Format->oformat;if (avio_open(&(pMp4Format->pb), OUT_FMT_FILE, AVIO_FLAG_READ_WRITE) < 0){return 0;}for (int i = 0; i < pFormat->nb_streams; i++) {AVStream *in_stream = pFormat->streams[i];AVStream *out_stream = avformat_new_stream(pMp4Format, in_stream->codec->codec);if (!out_stream) {return 0;}int ret = 0;ret = avcodec_copy_context(out_stream->codec, in_stream->codec);if (ret < 0) {fprintf(stderr, "Failed to copy context from input to output stream codec context\n");return 0;}out_stream->codec->codec_tag = 0;if (pMp4Format->oformat->flags & AVFMT_GLOBALHEADER)out_stream->codec->flags |= CODEC_FLAG_GLOBAL_HEADER;}av_dump_format(pMp4Format, 0, OUT_FMT_FILE, 1);if (avformat_write_header(pMp4Format, NULL) < 0){return 0;}av_opt_set(video_enc_ctx->priv_data, "preset", "superfast", 0);av_opt_set(video_enc_ctx->priv_data, "tune", "zerolatency", 0);avformat_write_header(pOFormat, NULL);AVPacket *pkt = new AVPacket();av_init_packet(pkt);AVFrame *pFrame = av_frame_alloc();// avcodec_alloc_frame();int ts = 0;while (1){if (av_read_frame(pFormat, pkt) < 0){avio_close(pOFormat->pb);av_write_trailer(pMp4Format);avio_close(pMp4Format->pb);delete pkt;return 0;}if (pkt->stream_index == 0){int got_picture = 0, ret = 0;ret = avcodec_decode_video2(video_dec_ctx, pFrame, &got_picture, pkt);if (ret < 0){delete pkt;return 0;}pFrame->pts = pFrame->pkt_pts;//ts++;if (got_picture){AVPacket *tmppkt = new AVPacket;av_init_packet(tmppkt);int size = video_enc_ctx->width*video_enc_ctx->height * 3 / 2;char* buf = new char[size];memset(buf, 0, size);tmppkt->data = (uint8_t*)buf;tmppkt->size = size;ret = avcodec_encode_video2(video_enc_ctx, tmppkt, pFrame, &got_picture);if (ret < 0){avio_close(pOFormat->pb);delete buf;return 0;}if (got_picture){//ret = av_interleaved_write_frame(pOFormat, tmppkt);AVStream *in_stream = pFormat->streams[pkt->stream_index];AVStream *out_stream = pMp4Format->streams[pkt->stream_index];tmppkt->pts = av_rescale_q_rnd(tmppkt->pts, in_stream->time_base, out_stream->time_base, AV_ROUND_NEAR_INF);tmppkt->dts = av_rescale_q_rnd(tmppkt->dts, in_stream->time_base, out_stream->time_base, AV_ROUND_NEAR_INF);tmppkt->duration = av_rescale_q(tmppkt->duration, in_stream->time_base, out_stream->time_base);tmppkt->pos = -1;ret = av_interleaved_write_frame(pMp4Format, tmppkt);if (ret < 0)return 0;delete tmppkt;delete buf;}}//avcodec_free_frame(&pFrame);}else if (pkt->stream_index == 1){AVStream *in_stream = pFormat->streams[pkt->stream_index];AVStream *out_stream = pMp4Format->streams[pkt->stream_index];pkt->pts = av_rescale_q_rnd(pkt->pts, in_stream->time_base, out_stream->time_base, AV_ROUND_NEAR_INF);pkt->dts = av_rescale_q_rnd(pkt->dts, in_stream->time_base, out_stream->time_base, AV_ROUND_NEAR_INF);pkt->duration = av_rescale_q(pkt->duration, in_stream->time_base, out_stream->time_base);pkt->pos = -1;if (av_interleaved_write_frame(pMp4Format, pkt) < 0)return 0;}}av_frame_free(&pFrame);return 0;}

工程下载地址（VC2013）：http://download.csdn.net/detail/wootengxjj/9559344。