FFmpeg简单转码程序

2022-06-11 20:45| 来源: 网络整理| 查看: 265

学习了雷神的文章，慕斯人分享精神，感其英年而逝，不胜唏嘘。他有分享一个转码程序《最简单的基于FFMPEG的转码程序》其中使用了filter（参考了ffmpeg.c中的流程），他曾说想再编写一个不需要filter的版本，可惜未有机会。恰好工作中有相关ffmpeg处理内容，故狗尾续貂，撰写本文。

相关流程：

1.打开输入文件

2.打开输出文件

3.设置解码环境

4.设置输出流信息

5.设置编码环境

6.打开输入流循环读取，解码再编码写入

7.fflush解码和编码ctx

8.关闭文件

本文的代码，为了支持视频精确剪辑，因为GOP关键帧问题，需要使用解码再编码，在编码中对时间做校验

使用方式：

./mycut input output start end

如，截取1到10秒的视频：

代码如下：

// mycut.cpp extern "C" { #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include // time_t, tm, time, localtime, strftime #include // time_t, tm, time, localtime, strftime } #define TIME_DEN 1000 // Returns the local date/time formatted as 2014-03-19 11:11:52 char* getFormattedTime(void); // Remove path from filename #define __SHORT_FILE__ (strrchr(__FILE__, '/') ? strrchr(__FILE__, '/') + 1 : __FILE__) // Main log macro //#define __LOG__(format, loglevel, ...) printf("%s %-5s [%s] [%s:%d] " format "\n", getFormattedTime(), loglevel, __func__, __SHORT_FILE__, __LINE__, ## __VA_ARGS__) #define __LOG__(format, loglevel, ...) printf("%ld %-5s [%s] [%s:%d] " format "\n", current_timestamp(), loglevel, __func__, __SHORT_FILE__, __LINE__, ## __VA_ARGS__) // Specific log macros with #define LOGDEBUG(format, ...) __LOG__(format, "DEBUG", ## __VA_ARGS__) #define LOGWARN(format, ...) __LOG__(format, "WARN", ## __VA_ARGS__) #define LOGERROR(format, ...) __LOG__(format, "ERROR", ## __VA_ARGS__) #define LOGINFO(format, ...) __LOG__(format, "INFO", ## __VA_ARGS__) // Returns the local date/time formatted as 2014-03-19 11:11:52 char* getFormattedTime(void) { time_t rawtime; struct tm* timeinfo; time(&rawtime); timeinfo = localtime(&rawtime); // Must be static, otherwise won't work static char _retval[26]; strftime(_retval, sizeof(_retval), "%Y-%m-%d %H:%M:%S", timeinfo); return _retval; } long long current_timestamp() { struct timeval te; gettimeofday(&te, NULL); // get current time long long milliseconds = te.tv_sec*1000LL + te.tv_usec/1000; // calculate milliseconds // printf("milliseconds: %lld\n", milliseconds); return milliseconds; } static int encode_and_save_pkt(AVCodecContext *enc_ctx, AVFormatContext *ofmt_ctx, AVStream *out_stream) { AVPacket enc_pkt; av_init_packet(&enc_pkt); enc_pkt.data = NULL; enc_pkt.size = 0; int ret = 0; while (ret >= 0) { ret = avcodec_receive_packet(enc_ctx, &enc_pkt); if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) { ret = 0; break; } else if (ret < 0) { printf("[avcodec_receive_packet]Error during encoding, ret:%d\n", ret); break; } LOGDEBUG("encode type:%d pts:%d dts:%d\n", enc_ctx->codec_type, enc_pkt.pts, enc_pkt.dts); /* rescale output packet timestamp values from codec to stream timebase */ av_packet_rescale_ts(&enc_pkt, enc_ctx->time_base, out_stream->time_base); enc_pkt.stream_index = out_stream->index; ret = av_interleaved_write_frame(ofmt_ctx, &enc_pkt); if (ret < 0) { printf("write frame error, ret:%d\n", ret); break; } av_packet_unref(&enc_pkt); } return ret; } static int decode_and_send_frame(AVCodecContext *dec_ctx, AVCodecContext *enc_ctx, int start, int end) { AVFrame *frame = av_frame_alloc(); int ret = 0; while (ret >= 0) { ret = avcodec_receive_frame(dec_ctx, frame); if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) { ret = 0; break; } else if (ret < 0) { printf("Error while receiving a frame from the decoder"); break; } int pts = frame->pts; LOGDEBUG("decode type:%d pts:%d\n", dec_ctx->codec_type, pts); if ((pts < start*TIME_DEN) || (pts > end*TIME_DEN)) { // 数据裁剪 continue; } frame->pict_type = AV_PICTURE_TYPE_NONE; // 修改pts frame->pts = pts - start*TIME_DEN; //printf("pts:%d\n", frame->pts); ret = avcodec_send_frame(enc_ctx, frame); if (ret < 0) { printf("Error sending a frame for encoding\n"); break; } } av_frame_free(&frame); return ret; } static int open_decodec_context(int *stream_idx, AVCodecContext **dec_ctx, AVFormatContext *fmt_ctx, enum AVMediaType type) { int ret, stream_index; AVStream *st; AVCodec *dec = NULL; AVDictionary *opts = NULL; ret = av_find_best_stream(fmt_ctx, type, -1, -1, &dec, 0); if (ret < 0) { fprintf(stderr, "Could not find %s stream in input file \n", av_get_media_type_string(type)); return ret; } else { stream_index = ret; st = fmt_ctx->streams[stream_index]; /* Allocate a codec context for the decoder */ *dec_ctx = avcodec_alloc_context3(dec); if (!*dec_ctx) { fprintf(stderr, "Failed to allocate the %s codec context\n", av_get_media_type_string(type)); return AVERROR(ENOMEM); } /* Copy codec parameters from input stream to output codec context */ if ((ret = avcodec_parameters_to_context(*dec_ctx, st->codecpar)) < 0) { fprintf(stderr, "Failed to copy %s codec parameters to decoder context\n", av_get_media_type_string(type)); return ret; } if ((*dec_ctx)->codec_type == AVMEDIA_TYPE_VIDEO) (*dec_ctx)->framerate = av_guess_frame_rate(fmt_ctx, st, NULL); /* Init the decoders, with or without reference counting */ av_dict_set_int(&opts, "refcounted_frames", 1, 0); if ((ret = avcodec_open2(*dec_ctx, dec, &opts)) < 0) { fprintf(stderr, "Failed to open %s codec\n", av_get_media_type_string(type)); return ret; } *stream_idx = stream_index; } return 0; } static int set_encode_option(AVCodecContext *dec_ctx, AVDictionary **opt) { const char *profile = avcodec_profile_name(dec_ctx->codec_id, dec_ctx->profile); if (profile) { if (!strcasecmp(profile, "high")) { av_dict_set(opt, "profile", "high", 0); } } else { av_dict_set(opt, "profile", "main", 0); } av_dict_set(opt, "threads", "16", 0); av_dict_set(opt, "preset", "slow", 0); av_dict_set(opt, "level", "4.0", 0); return 0; } static int open_encodec_context(int stream_index, AVCodecContext **oenc_ctx, AVFormatContext *fmt_ctx, enum AVMediaType type) { int ret; AVStream *st; AVCodec *encoder = NULL; AVDictionary *opts = NULL; AVCodecContext *enc_ctx; st = fmt_ctx->streams[stream_index]; /* find encoder for the stream */ encoder = avcodec_find_encoder(st->codecpar->codec_id); if (!encoder) { fprintf(stderr, "Failed to find %s codec\n", av_get_media_type_string(type)); return AVERROR(EINVAL); } enc_ctx = avcodec_alloc_context3(encoder); if (!enc_ctx) { printf("Failed to allocate the encoder context\n"); return AVERROR(ENOMEM); } AVCodecContext *dec_ctx = st->codec; if (type == AVMEDIA_TYPE_VIDEO) { enc_ctx->height = dec_ctx->height; enc_ctx->width = dec_ctx->width; enc_ctx->sample_aspect_ratio = dec_ctx->sample_aspect_ratio; enc_ctx->bit_rate = dec_ctx->bit_rate; enc_ctx->rc_max_rate = dec_ctx->bit_rate; enc_ctx->rc_buffer_size = dec_ctx->bit_rate; enc_ctx->bit_rate_tolerance = 0; // use yuv420P enc_ctx->pix_fmt = AV_PIX_FMT_YUV420P; // set frame rate enc_ctx->time_base.num = 1; enc_ctx->time_base.den = TIME_DEN; enc_ctx->flags |= AV_CODEC_FLAG_GLOBAL_HEADER; enc_ctx->has_b_frames = false; enc_ctx->max_b_frames = 0; enc_ctx->gop_size = 120; set_encode_option(dec_ctx, &opts); } else if (type == AVMEDIA_TYPE_AUDIO) { 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); /* take first format from list of supported formats */ enc_ctx->sample_fmt = encoder->sample_fmts[0]; enc_ctx->time_base = (AVRational){1, TIME_DEN}; enc_ctx->bit_rate = dec_ctx->bit_rate; enc_ctx->flags |= AV_CODEC_FLAG_GLOBAL_HEADER; } else { ret = avcodec_copy_context(enc_ctx, st->codec); if (ret < 0) { fprintf(stderr, "Failed to copy context from input to output stream codec context\n"); return ret; } } if ((ret = avcodec_open2(enc_ctx, encoder, &opts)) < 0) { fprintf(stderr, "Failed to open %s codec\n", av_get_media_type_string(type)); return ret; } *oenc_ctx = enc_ctx; return 0; } int test_cut(char *input_file, char *output_file, int start, int end) { int ret = 0; av_register_all(); // 输入流 AVFormatContext *ifmt_ctx = NULL; AVCodecContext *video_dec_ctx = NULL; AVCodecContext *audio_dec_ctx = NULL; char *flv_name = input_file; int video_stream_idx = 0; int audio_stream_idx = 1; // 输出流 AVFormatContext *ofmt_ctx = NULL; AVCodecContext *audio_enc_ctx = NULL; AVCodecContext *video_enc_ctx = NULL; if ((ret = avformat_open_input(&ifmt_ctx, flv_name, 0, 0)) < 0) { printf("Could not open input file '%s' ret:%d\n", flv_name, ret); goto end; } if ((ret = avformat_find_stream_info(ifmt_ctx, 0)) < 0) { printf("Failed to retrieve input stream information"); goto end; } if (open_decodec_context(&video_stream_idx, &video_dec_ctx, ifmt_ctx, AVMEDIA_TYPE_VIDEO) < 0) { printf("fail to open vedio decode context, ret:%d\n", ret); goto end; } if (open_decodec_context(&audio_stream_idx, &audio_dec_ctx, ifmt_ctx, AVMEDIA_TYPE_AUDIO) < 0) { printf("fail to open audio decode context, ret:%d\n", ret); goto end; } av_dump_format(ifmt_ctx, 0, input_file, 0); // 设置输出 avformat_alloc_output_context2(&ofmt_ctx, NULL, NULL, output_file); if (!ofmt_ctx) { printf("can not open ouout context"); goto end; } // video stream AVStream *out_stream; out_stream = avformat_new_stream(ofmt_ctx, NULL); if (!out_stream) { printf("Failed allocating output stream\n"); ret = AVERROR_UNKNOWN; goto end; } if ((ret = open_encodec_context(video_stream_idx, &video_enc_ctx, ifmt_ctx, AVMEDIA_TYPE_VIDEO)) < 0) { printf("video enc ctx init err\n"); goto end; } ret = avcodec_parameters_from_context(out_stream->codecpar, video_enc_ctx); if (ret < 0) { printf("Failed to copy codec parameters\n"); goto end; } video_enc_ctx->flags |= AV_CODEC_FLAG_GLOBAL_HEADER; out_stream->time_base = video_enc_ctx->time_base; out_stream->codecpar->codec_tag = 0; // audio stream out_stream = avformat_new_stream(ofmt_ctx, NULL); if (!out_stream) { printf("Failed allocating output stream\n"); ret = AVERROR_UNKNOWN; goto end; } if ((ret = open_encodec_context(audio_stream_idx, &audio_enc_ctx, ifmt_ctx, AVMEDIA_TYPE_AUDIO)) < 0) { printf("audio enc ctx init err\n"); goto end; } ret = avcodec_parameters_from_context(out_stream->codecpar, audio_enc_ctx); if (ret < 0) { printf("Failed to copy codec parameters\n"); goto end; } audio_enc_ctx->flags |= AV_CODEC_FLAG_GLOBAL_HEADER; out_stream->time_base = audio_enc_ctx->time_base; out_stream->codecpar->codec_tag = 0; av_dump_format(ofmt_ctx, 0, output_file, 1); // 打开文件 if (!(ofmt_ctx->oformat->flags & AVFMT_NOFILE)) { ret = avio_open(&ofmt_ctx->pb, output_file, AVIO_FLAG_WRITE); if (ret < 0) { printf("Could not open output file '%s'\n", output_file); goto end; } } ret = avformat_write_header(ofmt_ctx, NULL); if (ret < 0) { printf("Error occurred when opening output file\n"); goto end; } AVPacket flv_pkt; int stream_index; while (1) { AVPacket *pkt = &flv_pkt; ret = av_read_frame(ifmt_ctx, pkt); if (ret < 0) { break; } if (pkt->stream_index == video_stream_idx && (pkt->flags & AV_PKT_FLAG_KEY)) { printf("pkt.dts = %ld pkt.pts = %ld pkt.stream_index = %d is key frame\n", pkt->dts, pkt->pts, pkt->stream_index); } stream_index = pkt->stream_index; if (pkt->stream_index == video_stream_idx) { ret = avcodec_send_packet(video_dec_ctx, pkt); LOGDEBUG("read type:%d pts:%d dts:%d\n", video_dec_ctx->codec_type, pkt->pts, pkt->dts); ret = decode_and_send_frame(video_dec_ctx, video_enc_ctx, start, end); ret = encode_and_save_pkt(video_enc_ctx, ofmt_ctx, ofmt_ctx->streams[0]); if (ret < 0) { printf("re encode video error, ret:%d\n", ret); } } else if (pkt->stream_index == audio_stream_idx) { ret = avcodec_send_packet(audio_dec_ctx, pkt); LOGDEBUG("read type:%d pts:%d dts:%d\n", audio_dec_ctx->codec_type, pkt->pts, pkt->dts); ret = decode_and_send_frame(audio_dec_ctx, audio_enc_ctx, start, end); ret = encode_and_save_pkt(audio_enc_ctx, ofmt_ctx, ofmt_ctx->streams[1]); if (ret < 0) { printf("re encode audio error, ret:%d\n", ret); } } av_packet_unref(pkt); } // fflush // fflush encode avcodec_send_packet(video_dec_ctx, NULL); decode_and_send_frame(video_dec_ctx, video_enc_ctx, start, end); avcodec_send_packet(audio_dec_ctx, NULL); decode_and_send_frame(audio_dec_ctx, audio_enc_ctx, start, end); // fflush decode avcodec_send_frame(video_enc_ctx, NULL); encode_and_save_pkt(video_enc_ctx, ofmt_ctx, ofmt_ctx->streams[0]); avcodec_send_frame(audio_enc_ctx, NULL); encode_and_save_pkt(audio_enc_ctx, ofmt_ctx, ofmt_ctx->streams[1]); LOGDEBUG("stream end\n"); av_write_trailer(ofmt_ctx); end: avformat_close_input(&ifmt_ctx); if (ofmt_ctx && !(ofmt_ctx->oformat->flags & AVFMT_NOFILE)) avio_closep(&ofmt_ctx->pb); avformat_free_context(ofmt_ctx); avcodec_free_context(&video_dec_ctx); avcodec_free_context(&audio_dec_ctx); return ret; } int main(int argc, char **argv) { int ret = 0; if (argc < 5) { printf("Usage: %s input output start end \n", argv[0]); return 1; } char *input_file = argv[1]; char *output_file = argv[2]; int start = atoi(argv[3]); int end = atoi(argv[4]); ret = test_cut(input_file, output_file, start, end); return ret; }

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FFmpeg简单转码程序

FFmpeg简单转码程序

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