FFMPEG实现的转码程序
本例子是由FFEMPG的doc/example例子transcode.c修改而来,可以根据需求任意转换音视频的编码。
原来的例子的作用更类似于remux,并没有实现转码的功能,只是实现了格式转换,比如ts转avi等。并不能实现音视频编码格式的转换,比如将h264转为mpeg2。
FFMPEG转码的实现有多种方式:
一种方式是:流解复用->视频+音频流->解码->YUV/PCM等->视音频编码->重新生成的音视频流->复用->流
另一种方式依赖AVFilter,这一部分在另外的几篇文章中解释怎么用。虽然AVFilter学习起来可能比较困难,但是在实际的编程应用中,依靠AVFilter做转码效率比第一种方式高,并且解码的CPU和时间消耗也少的多。所以,还是建议好好学习这部分的,毕竟我一直觉得FFMPEG的强项就是解码和转码。
本例子是视频mpeg2转h264,音频mpegaudio转g711。
- <span style="font-family:SimHei;font-size:18px;">/*
- * based on FFMPEG transcode.c
- * modified by tongli
- */
- #include <stdio.h>
- #include "snprintf.h"
- extern "C"
- {
- #include <libavcodec/avcodec.h>
- #include <libavformat/avformat.h>
- #include <libavfilter/avfiltergraph.h>
- #include <libavfilter/avcodec.h>
- #include <libavfilter/buffersink.h>
- #include <libavfilter/buffersrc.h>
- #include <libavutil/opt.h>
- #include <libavutil/pixdesc.h>
- }
- static AVFormatContext *ifmt_ctx;
- static AVFormatContext *ofmt_ctx;
- typedef struct FilteringContext {
- AVFilterContext *buffersink_ctx;
- AVFilterContext *buffersrc_ctx;
- AVFilterGraph *filter_graph;
- } FilteringContext;
- static FilteringContext *filter_ctx;
- 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, NULL, 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 = 16;
- enc_ctx->max_qdiff = 4;
- enc_ctx->qmin = 10;
- enc_ctx->qmax = 51;
- enc_ctx->qcompress = 0.6;
- enc_ctx->refs = 3;
- enc_ctx->bit_rate = 500000;
- 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 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_PCM_ALAW);
- 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 init_filter(FilteringContext* fctx, AVCodecContext *dec_ctx,
- AVCodecContext *enc_ctx, const char *filter_spec)
- {
- char args[512];
- int ret = 0;
- AVFilter *buffersrc = NULL;
- AVFilter *buffersink = NULL;
- AVFilterContext *buffersrc_ctx = NULL;
- AVFilterContext *buffersink_ctx = NULL;
- AVFilterInOut *outputs = avfilter_inout_alloc();
- AVFilterInOut *inputs = avfilter_inout_alloc();
- AVFilterGraph *filter_graph = avfilter_graph_alloc();
- if (!outputs || !inputs || !filter_graph) {
- ret = AVERROR(ENOMEM);
- goto end;
- }
- if (dec_ctx->codec_type == AVMEDIA_TYPE_VIDEO) {
- buffersrc = avfilter_get_by_name("buffer");
- buffersink = avfilter_get_by_name("buffersink");
- if (!buffersrc || !buffersink) {
- av_log(NULL, AV_LOG_ERROR, "filtering source or sink element not found\n");
- ret = AVERROR_UNKNOWN;
- goto end;
- }
- snprintf(args, sizeof(args),
- "video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d",
- dec_ctx->width, dec_ctx->height, dec_ctx->pix_fmt,
- dec_ctx->time_base.num, dec_ctx->time_base.den,
- dec_ctx->sample_aspect_ratio.num,
- dec_ctx->sample_aspect_ratio.den);
- ret = avfilter_graph_create_filter(&buffersrc_ctx, buffersrc, "in",
- args, NULL, filter_graph);
- if (ret < 0) {
- av_log(NULL, AV_LOG_ERROR, "Cannot create buffer source\n");
- goto end;
- }
- ret = avfilter_graph_create_filter(&buffersink_ctx, buffersink, "out",
- NULL, NULL, filter_graph);
- if (ret < 0) {
- av_log(NULL, AV_LOG_ERROR, "Cannot create buffer sink\n");
- goto end;
- }
- ret = av_opt_set_bin(buffersink_ctx, "pix_fmts",
- (uint8_t*)&enc_ctx->pix_fmt, sizeof(enc_ctx->pix_fmt),
- AV_OPT_SEARCH_CHILDREN);
- if (ret < 0) {
- av_log(NULL, AV_LOG_ERROR, "Cannot set output pixel format\n");
- goto end;
- }
- }
- else if (dec_ctx->codec_type == AVMEDIA_TYPE_AUDIO) {
- buffersrc = avfilter_get_by_name("abuffer");
- buffersink = avfilter_get_by_name("abuffersink");
- if (!buffersrc || !buffersink) {
- av_log(NULL, AV_LOG_ERROR, "filtering source or sink element not found\n");
- ret = AVERROR_UNKNOWN;
- goto end;
- }
- if (!dec_ctx->channel_layout)
- dec_ctx->channel_layout =
- av_get_default_channel_layout(dec_ctx->channels);
- snprintf(args, sizeof(args),
- "time_base=%d/%d:sample_rate=%d:sample_fmt=%s:channel_layout=0x%"PRIx64,
- dec_ctx->time_base.num, dec_ctx->time_base.den, dec_ctx->sample_rate,
- av_get_sample_fmt_name(dec_ctx->sample_fmt),
- dec_ctx->channel_layout);
- ret = avfilter_graph_create_filter(&buffersrc_ctx, buffersrc, "in",
- args, NULL, filter_graph);
- if (ret < 0) {
- av_log(NULL, AV_LOG_ERROR, "Cannot create audio buffer source\n");
- goto end;
- }
- ret = avfilter_graph_create_filter(&buffersink_ctx, buffersink, "out",
- NULL, NULL, filter_graph);
- if (ret < 0) {
- av_log(NULL, AV_LOG_ERROR, "Cannot create audio buffer sink\n");
- goto end;
- }
- ret = av_opt_set_bin(buffersink_ctx, "sample_fmts",
- (uint8_t*)&enc_ctx->sample_fmt, sizeof(enc_ctx->sample_fmt),
- AV_OPT_SEARCH_CHILDREN);
- if (ret < 0) {
- av_log(NULL, AV_LOG_ERROR, "Cannot set output sample format\n");
- goto end;
- }
- ret = av_opt_set_bin(buffersink_ctx, "channel_layouts",
- (uint8_t*)&enc_ctx->channel_layout,
- sizeof(enc_ctx->channel_layout), AV_OPT_SEARCH_CHILDREN);
- if (ret < 0) {
- av_log(NULL, AV_LOG_ERROR, "Cannot set output channel layout\n");
- goto end;
- }
- ret = av_opt_set_bin(buffersink_ctx, "sample_rates",
- (uint8_t*)&enc_ctx->sample_rate, sizeof(enc_ctx->sample_rate),
- AV_OPT_SEARCH_CHILDREN);
- if (ret < 0) {
- av_log(NULL, AV_LOG_ERROR, "Cannot set output sample rate\n");
- goto end;
- }
- }
- else {
- ret = AVERROR_UNKNOWN;
- goto end;
- }
- /* Endpoints for the filter graph. */
- outputs->name = av_strdup("in");
- outputs->filter_ctx = buffersrc_ctx;
- outputs->pad_idx = 0;
- outputs->next = NULL;
- inputs->name = av_strdup("out");
- inputs->filter_ctx = buffersink_ctx;
- inputs->pad_idx = 0;
- inputs->next = NULL;
- if (!outputs->name || !inputs->name) {
- ret = AVERROR(ENOMEM);
- goto end;
- }
- if ((ret = avfilter_graph_parse_ptr(filter_graph, filter_spec,
- &inputs, &outputs, NULL)) < 0)
- goto end;
- if ((ret = avfilter_graph_config(filter_graph, NULL)) < 0)
- goto end;
- /* Fill FilteringContext */
- fctx->buffersrc_ctx = buffersrc_ctx;
- fctx->buffersink_ctx = buffersink_ctx;
- fctx->filter_graph = filter_graph;
- end:
- avfilter_inout_free(&inputs);
- avfilter_inout_free(&outputs);
- return ret;
- }
- static int init_filters(void)
- {
- const char *filter_spec;
- unsigned int i;
- int ret;
- filter_ctx = (FilteringContext*)av_malloc_array(ifmt_ctx->nb_streams, sizeof(*filter_ctx));
- if (!filter_ctx)
- return AVERROR(ENOMEM);
- for (i = 0; i < ifmt_ctx->nb_streams; i++) {
- filter_ctx[i].buffersrc_ctx = NULL;
- filter_ctx[i].buffersink_ctx = NULL;
- filter_ctx[i].filter_graph = NULL;
- if (!(ifmt_ctx->streams[i]->codec->codec_type == AVMEDIA_TYPE_AUDIO
- || ifmt_ctx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO))
- continue;
- if (ifmt_ctx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO)
- filter_spec = "null"; /* passthrough (dummy) filter for video */
- else
- filter_spec = "anull"; /* passthrough (dummy) filter for audio */
- ret = init_filter(&filter_ctx[i], ifmt_ctx->streams[i]->codec,
- ofmt_ctx->streams[i]->codec, filter_spec);
- if (ret)
- return ret;
- }
- return 0;
- }
- static int encode_write_frame(AVFrame *filt_frame, unsigned int stream_index, int *got_frame) {
- 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);
- av_frame_free(&filt_frame);
- if (ret < 0)
- return ret;
- if (!(*got_frame))
- return 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);
- 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 filter_encode_write_frame(AVFrame *frame, unsigned int stream_index)
- {
- int ret;
- AVFrame *filt_frame;
- av_log(NULL, AV_LOG_INFO, "Pushing decoded frame to filters\n");
- /* push the decoded frame into the filtergraph */
- ret = av_buffersrc_add_frame_flags(filter_ctx[stream_index].buffersrc_ctx,
- frame, 0);
- if (ret < 0) {
- av_log(NULL, AV_LOG_ERROR, "Error while feeding the filtergraph\n");
- return ret;
- }
- /* pull filtered frames from the filtergraph */
- while (1) {
- filt_frame = av_frame_alloc();
- if (!filt_frame) {
- ret = AVERROR(ENOMEM);
- break;
- }
- av_log(NULL, AV_LOG_INFO, "Pulling filtered frame from filters\n");
- ret = av_buffersink_get_frame(filter_ctx[stream_index].buffersink_ctx,
- filt_frame);
- if (ret < 0) {
- /* if no more frames for output - returns AVERROR(EAGAIN)
- * if flushed and no more frames for output - returns AVERROR_EOF
- * rewrite retcode to 0 to show it as normal procedure completion
- */
- if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
- ret = 0;
- av_frame_free(&filt_frame);
- break;
- }
- filt_frame->pict_type = AV_PICTURE_TYPE_NONE;
- ret = encode_write_frame(filt_frame, stream_index, NULL);
- if (ret < 0)
- break;
- }
- return ret;
- }
- static int flush_encoder(unsigned int stream_index)
- {
- int ret;
- int got_frame;
- if (!(ofmt_ctx->streams[stream_index]->codec->codec->capabilities &
- CODEC_CAP_DELAY))
- return 0;
- while (1) {
- 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.ts")) < 0)
- goto end;
- if ((ret = open_output_file("test.avi")) < 0)
- goto end;
- if ((ret = init_filters()) < 0)
- goto end;
- /* read all packets */
- 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);
- if (filter_ctx[stream_index].filter_graph) {
- 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 = av_frame_get_best_effort_timestamp(frame);
- ret = filter_encode_write_frame(frame, stream_index);
- av_frame_free(&frame);
- if (ret < 0)
- goto end;
- }
- else {
- av_frame_free(&frame);
- }
- }
- else {
- /* remux this frame without reencoding */
- av_packet_rescale_ts(&packet,
- ifmt_ctx->streams[stream_index]->time_base,
- ofmt_ctx->streams[stream_index]->time_base);
- ret = av_interleaved_write_frame(ofmt_ctx, &packet);
- if (ret < 0)
- goto end;
- }
- av_free_packet(&packet);
- }
- /* flush filters and encoders */
- for (i = 0; i < ifmt_ctx->nb_streams; i++) {
- /* flush filter */
- if (!filter_ctx[i].filter_graph)
- continue;
- ret = filter_encode_write_frame(NULL, i);
- if (ret < 0) {
- av_log(NULL, AV_LOG_ERROR, "Flushing filter failed\n");
- goto end;
- }
- /* flush encoder */
- ret = flush_encoder(i);
- if (ret < 0) {
- av_log(NULL, AV_LOG_ERROR, "Flushing encoder failed\n");
- goto end;
- }
- }
- av_write_trailer(ofmt_ctx);
- end:
- av_free_packet(&packet);
- av_frame_free(&frame);
- 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);
- if (filter_ctx && filter_ctx[i].filter_graph)
- avfilter_graph_free(&filter_ctx[i].filter_graph);
- }
- 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));
- return ret ? 1 : 0;
- }
- </span>
源代码下载:
csdn工程:http://download.csdn.NET/detail/rootusers/8425619
from:http://blog.csdn.net/rootusers/article/details/43488827
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