FFmpeg Transcode(转码)

2024-04-23 17:48
文章标签 ffmpeg 转码 transcode

本文主要是介绍FFmpeg Transcode(转码)，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

本文基于官方例子：doc/examples/transcoding.c 。

流程

其中，AVFormatContext、AVPacket等重要的结构体请看：FFmpeg重要结构体（转自雷神） 。

与FFmpeg 简单实现转码 差异性如下：

1.增加Filter（滤镜）处理

具体请看FFmpeg Filter和SDL（Video） 和 FFmpeg Filter和SDL（Audio）

2.优化SwrContext（重采样）处理

关键理解是这一段：

//1.swr_get_out_samples
if (swr_get_out_samples(swr_ctx, 0) >= enc_ctx->frame_size) {//当上次缓存足够时，取缓存//2.swr_convertif ((ret = swr_convert(swr_ctx, reasampling_frame->data, enc_ctx->frame_size, NULL, 0)) < 0) {fprintf(stderr, "resampling cache failed\n");goto end;}fprintf(stdout, "resampling cache\n");
} else {//进行重采样 //3.swr_convertif ((ret = swr_convert(swr_ctx, reasampling_frame->data, enc_ctx->frame_size,(const uint8_t **) filt_frame->data,filt_frame->nb_samples)) < 0) {fprintf(stderr, "resampling data failed\n");goto end;}
}

1.swr_get_out_samples 含义：获取当前采样缓存的大小。

2.swr_convert 含义：从采样缓存中采样enc_ctx->frame_size个长度数据到reasampling_frame->data中。

3.swr_convert 含义：从有个filt_frame->nb_samples数据的filt_frame->data中采样enc_ctx->frame_size个长度数据到reasampling_frame->data中。

3.增加AVAudioFifo缓存处理

主要有三个方法av_audio_fifo_size 、 av_audio_fifo_write 和av_audio_fifo_read ，详细见代码。

4.视频和音频同步

1.创建流时(avformat_new_stream)，初始化时间基out_stream->time_base = enc_ctx->time_base 。

2.送去解码前，需要重新计算pts、dts和duration，代码如下：

av_packet_rescale_ts(de_pkt,ifmt_ctx->streams[stream_index]->time_base,ifmt_ctx->streams[stream_index]->codec->time_base);

3.送去编码前，计算pts、dts和duration，代码如下：

av_packet_rescale_ts(enc_pkt,ofmt_ctx->streams[stream_index]->codec->time_base,ofmt_ctx->streams[stream_index]->time_base);

4.注意：当音频编码器的frame_size和需要被编码的AVFrame中的nb_samples 大小不相等时，需要使用重采样或使用AVAudioFifo缓存，使得frame_size == nb_samples后再送去编码，这种情况会导致pts、dts和duration的值与其他帧相同问题。

if (stream_index == AVMEDIA_TYPE_AUDIO && filt_frame->nb_samples != enc_ctx->frame_size){......
}

代码实现

extern "C" {
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libavfilter/buffersink.h>
#include <libavfilter/buffersrc.h>
#include <libavutil/opt.h>
#include <libavutil/pixdesc.h>
#include <libswresample/swresample.h>
#include "libavutil/audio_fifo.h"
}//将每一组滤镜组合放到一起，filter_stm[i]和ifmt_ctx->streams[i]下标保持一致，表示对音频或者视频的滤镜
typedef struct FilterStream {AVFilterContext *buffersink_ctx;AVFilterContext *buffersrc_ctx;AVFilterGraph *filter_graph;
} FilterStream;static FilterStream *filter_stm;
static AVFormatContext *ifmt_ctx;
static AVFormatContext *ofmt_ctx;
static int audio_index, video_index;
static SwrContext *swr_ctx;//音频：当有需要时，需要重采样
static int64_t resample_pos = 0;//重采样时，会有缓存，这时候要另外计算dts和pts
static AVAudioFifo *fifo = NULL;;//重采样时，如果输入nb_sample比输出的nb_sample小时，需要缓存int open_input_file(const char *in_filename) {int ret = -1, i;/**（解封装 1.1）：创建并初始化AVFormatContext*/if (avformat_open_input(&ifmt_ctx, in_filename, NULL, NULL) < 0) {fprintf(stderr, "Could not open source file %s\n", in_filename);goto end;}/**（解封装 1.2）：检索流信息，这个过程会检查输入流中信息是否存在异常*/if (avformat_find_stream_info(ifmt_ctx, NULL) < 0) {fprintf(stderr, "Could not find stream information\n");goto end;}for (i = 0; i < ifmt_ctx->nb_streams; i++) {AVStream *stream = ifmt_ctx->streams[i];AVCodec *dec;AVCodecContext *dec_ctx;//dec_ctx = stream->codec; //-->通过这种形式获取的解码器上下文已过时/**（解码 2.1）：查找解码器(AVCodec)*/if (!(dec = avcodec_find_decoder(stream->codecpar->codec_id))) {fprintf(stderr, "Failed to find decoder for stream #%u\n", i);ret = AVERROR_DECODER_NOT_FOUND;goto end;}/**（解码 2.2）：通过解码器(AVCodec)生成解码器上下文(AVCodecContext)*/if (!(dec_ctx = avcodec_alloc_context3(dec))) {fprintf(stderr, "Failed to allocate the decoder context for stream #%u\n", i);ret = AVERROR(ENOMEM);goto end;}/**（解码 2.3）：将AVCodecParameters参数赋值给AVCodecContext*/if ((ret = avcodec_parameters_to_context(dec_ctx, stream->codecpar)) < 0) {fprintf(stderr, "Failed to copy decoder parameters to input decoder context for stream #%u\n", i);goto end;}/* Reencode video & audio and remux subtitles etc. */if (dec_ctx->codec_type == AVMEDIA_TYPE_VIDEO || dec_ctx->codec_type == AVMEDIA_TYPE_AUDIO) {if (dec_ctx->codec_type == AVMEDIA_TYPE_VIDEO) {dec_ctx->framerate = av_guess_frame_rate(ifmt_ctx, stream, NULL);video_index = i;} else if (dec_ctx->codec_type == AVMEDIA_TYPE_AUDIO) {audio_index = i;}/**（解码 2.4）：初始化码器器上下文*/if ((ret = avcodec_open2(dec_ctx, dec, NULL)) < 0) {fprintf(stderr, "Failed to open decoder for stream #%u\n", i);goto end;}}//替换掉原来的，后面可以直接取了stream->codec = dec_ctx;}//打印输出日志
//    fprintf(stderr, "---------------------------ifmt_ctx----------------\n");
//    av_dump_format(ifmt_ctx, 0, in_filename, 0);ret = 0;end:return ret;
}int open_output_file(const char *out_filename) {int ret = -1, i;AVStream *out_stream, *in_stream;AVCodecContext *dec_ctx, *enc_ctx;AVCodec *encoder;AVCodecID encodec_id;/**（封装 4.1）：根据文件格式初始化封装器上下文AVFormatContext*/avformat_alloc_output_context2(&ofmt_ctx, NULL, NULL, out_filename);if (!ofmt_ctx) {fprintf(stderr, "Could not create output context\n");ret = AVERROR_UNKNOWN;goto end;}for (i = 0; i < ifmt_ctx->nb_streams; i++) {/**（封装 4.2）：创建输出视频和音频AVStream*/if (!(out_stream = avformat_new_stream(ofmt_ctx, NULL))) {fprintf(stderr, "Failed allocating output stream\n");ret = AVERROR_UNKNOWN;goto end;}out_stream->codecpar->codec_tag = 0;in_stream = ifmt_ctx->streams[i];dec_ctx = in_stream->codec;if (dec_ctx->codec_type == AVMEDIA_TYPE_VIDEO|| dec_ctx->codec_type == AVMEDIA_TYPE_AUDIO) {if (dec_ctx->codec_type == AVMEDIA_TYPE_VIDEO) {encodec_id = ofmt_ctx->oformat->video_codec;} else if (dec_ctx->codec_type == AVMEDIA_TYPE_AUDIO) {encodec_id = ofmt_ctx->oformat->audio_codec;}/* in this example, we choose transcoding to same codec *//**（编码 3.1）：获取对应的编码器AVCodec*/if (!(encoder = avcodec_find_encoder(encodec_id))) {fprintf(stderr, "Necessary encoder not found\n");ret = AVERROR_INVALIDDATA;goto end;}/**（编码 3.2）：通过编码器(AVCodec)获取编码器上下文(AVCodecContext)*/if (!(enc_ctx = avcodec_alloc_context3(encoder))) {fprintf(stderr, "Failed to allocate the encoder context\n");ret = AVERROR(ENOMEM);goto end;}/**给编码器初始化信息*//* In this example, we transcode to same properties (picture size,* sample rate etc.). These properties can be changed for output* streams easily using filters */if (dec_ctx->codec_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;//take first format from list of supported formatsif (encoder->pix_fmts)enc_ctx->pix_fmt = encoder->pix_fmts[0];elseenc_ctx->pix_fmt = dec_ctx->pix_fmt;//video time_base can be set to whatever is handy and supported by encoderenc_ctx->time_base = dec_ctx->time_base;enc_ctx->has_b_frames = dec_ctx->has_b_frames;//输出将相对于输入延迟max_b_frames + 1-->但是输入的为0！//enc_ctx->max_b_frames = dec_ctx->max_b_frames + 1;enc_ctx->max_b_frames = 2;enc_ctx->bit_rate = dec_ctx->bit_rate;enc_ctx->codec_type = dec_ctx->codec_type;//不支持B帧if (enc_ctx->max_b_frames &&enc_ctx->codec_id != AV_CODEC_ID_MPEG4 &&enc_ctx->codec_id != AV_CODEC_ID_MPEG1VIDEO &&enc_ctx->codec_id != AV_CODEC_ID_MPEG2VIDEO) {enc_ctx->has_b_frames = 0;enc_ctx->max_b_frames = 0;}} else {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(dec_ctx->channel_layout);enc_ctx->sample_fmt = encoder->sample_fmts[0];enc_ctx->time_base = {1, enc_ctx->sample_rate};enc_ctx->bit_rate = dec_ctx->bit_rate;enc_ctx->codec_type = dec_ctx->codec_type;}if (ofmt_ctx->oformat->flags & AVFMT_GLOBALHEADER)enc_ctx->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;/**（编码 3.3）：*//* Third parameter can be used to pass settings to encoder */if ((ret = avcodec_open2(enc_ctx, encoder, NULL)) < 0) {fprintf(stderr, "Cannot open video encoder for stream #%u\n", i);goto end;}/**（编码 3.4）：*/if ((ret = avcodec_parameters_from_context(out_stream->codecpar, enc_ctx)) < 0) {fprintf(stderr, "Failed to copy encoder parameters to output stream #%u\n", i);goto end;}out_stream->time_base = enc_ctx->time_base;//替换掉旧的out_stream->codec = enc_ctx;} else if (dec_ctx->codec_type == AVMEDIA_TYPE_UNKNOWN) {fprintf(stderr, "Elementary stream #%d is of unknown type, cannot proceed\n", i);ret = AVERROR_INVALIDDATA;goto end;} else {/* if this stream must be remuxed */if ((ret = avcodec_parameters_copy(out_stream->codecpar, in_stream->codecpar)) < 0) {fprintf(stderr, "Copying parameters for stream #%u failed\n", i);goto end;}out_stream->time_base = in_stream->time_base;}}//打印输出日志
//    fprintf(stderr, "---------------------------ofmt_ctx----------------\n");
//    av_dump_format(ofmt_ctx, 0, out_filename, 1);/**（封装 4.4）：初始化AVIOContext*/if (!(ofmt_ctx->oformat->flags & AVFMT_NOFILE)) { ;if ((ret = avio_open(&ofmt_ctx->pb, out_filename, AVIO_FLAG_WRITE)) < 0) {fprintf(stderr, "Could not open output file '%s'", out_filename);goto end;}}/**（封装 4.5）：写入文件头*//* init muxer, write output file header */if ((ret = avformat_write_header(ofmt_ctx, NULL)) < 0) {fprintf(stderr, "Error occurred when opening output file\n");goto end;}ret = 0;end:return ret;
}int init_resampling() {AVCodecContext *dec_ctx_audio = ifmt_ctx->streams[audio_index]->codec;AVCodecContext *enc_ctx_audio = ofmt_ctx->streams[audio_index]->codec;int ret = -1;/**（重采样 5.1）：申请内存*/if (!(swr_ctx = swr_alloc())) {fprintf(stderr, "Could not allocate resampler context\n");return ret;}/**（重采样 5.2）：设置参数*/av_opt_set_int(swr_ctx, "in_channel_count", dec_ctx_audio->channels, 0);av_opt_set_int(swr_ctx, "in_sample_rate", dec_ctx_audio->sample_rate, 0);av_opt_set_sample_fmt(swr_ctx, "in_sample_fmt", dec_ctx_audio->sample_fmt, 0);av_opt_set_int(swr_ctx, "out_channel_count", enc_ctx_audio->channels, 0);av_opt_set_int(swr_ctx, "out_sample_rate", enc_ctx_audio->sample_rate, 0);av_opt_set_sample_fmt(swr_ctx, "out_sample_fmt", enc_ctx_audio->sample_fmt, 0);/**（重采样 5.3）：初始化SwrContext*/if ((ret = swr_init(swr_ctx)) < 0) {fprintf(stderr, "Failed to initialize the resampling context\n");return ret;}return 0;
}int init_filter(FilterStream *fctx, AVCodecContext *dec_ctx, AVCodecContext *enc_ctx, const char *filter_spec) {char args[512];int ret = 0;const AVFilter *buffersrc = NULL;const 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);fprintf(stderr, "Filter alloc failed\n");goto end;}if (dec_ctx->codec_type == AVMEDIA_TYPE_VIDEO) {/**（滤镜 6.1）：获取输入和输出滤镜器【同音频】*/buffersrc = avfilter_get_by_name("buffer");buffersink = avfilter_get_by_name("buffersink");if (!buffersrc || !buffersink) {fprintf(stderr, "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);/**（滤镜 6.2）：创建和初始化输入和输出过滤器实例并将其添加到现有图形中*/if ((ret = avfilter_graph_create_filter(&buffersrc_ctx, buffersrc, "in", args, NULL, filter_graph)) < 0) {fprintf(stderr, "Cannot create buffer source\n");goto end;}if ((ret = avfilter_graph_create_filter(&buffersink_ctx, buffersink, "out", NULL, NULL, filter_graph)) < 0) {fprintf(stderr, "Cannot create buffer sink\n");goto end;}/**（滤镜 6.3）：给【输出】滤镜器上下文设置参数*///如：val = {AV_PIX_FMT_YUV420P, AV_PIX_FMT_NONE};//注意输入的格式类型 val[0]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) {fprintf(stderr, "Cannot set output pixel format\n");goto end;}} else if (dec_ctx->codec_type == AVMEDIA_TYPE_AUDIO) {buffersrc = avfilter_get_by_name("abuffer");//名称比视频的前面多一个abuffersink = avfilter_get_by_name("abuffersink");if (!buffersrc || !buffersink) {fprintf(stderr, "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%lld",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);if ((ret = avfilter_graph_create_filter(&buffersrc_ctx, buffersrc, "in", args, NULL, filter_graph)) < 0) {fprintf(stderr, "Cannot create audio buffer source\n");goto end;}if ((ret = avfilter_graph_create_filter(&buffersink_ctx, buffersink, "out", NULL, NULL, filter_graph)) < 0) {fprintf(stderr, "Cannot create audio buffer sink\n");goto end;}if ((ret = av_opt_set_bin(buffersink_ctx, "sample_fmts",(uint8_t *) &enc_ctx->sample_fmt, sizeof(enc_ctx->sample_fmt),AV_OPT_SEARCH_CHILDREN)) < 0) {fprintf(stderr, "Cannot set output sample format\n");goto end;}if ((ret = av_opt_set_bin(buffersink_ctx, "channel_layouts",(uint8_t *) &enc_ctx->channel_layout, sizeof(enc_ctx->channel_layout),AV_OPT_SEARCH_CHILDREN)) < 0) {fprintf(stderr, "Cannot set output channel layout\n");goto end;}if ((ret = av_opt_set_bin(buffersink_ctx, "sample_rates",(uint8_t *) &enc_ctx->sample_rate, sizeof(enc_ctx->sample_rate),AV_OPT_SEARCH_CHILDREN)) < 0) {fprintf(stderr, "Cannot set output sample rate\n");goto end;}} else {ret = AVERROR_UNKNOWN;fprintf(stderr, "Filter input unknown stream\n");goto end;}//绑定关系 in ——> buffersrc_ctx/* Endpoints for the filter graph. */outputs->name = av_strdup("in");outputs->filter_ctx = buffersrc_ctx;outputs->pad_idx = 0;outputs->next = NULL;//绑定关系 out ——> buffersink_ctxinputs->name = av_strdup("out");inputs->filter_ctx = buffersink_ctx;inputs->pad_idx = 0;inputs->next = NULL;if (!outputs->name || !inputs->name) {ret = AVERROR(ENOMEM);fprintf(stderr, "Filter av_strdup name failed\n");goto end;}/**（滤镜 6.4）：将字符串描述的图形添加到图形中*/if ((ret = avfilter_graph_parse_ptr(filter_graph, filter_spec, &inputs, &outputs, NULL)) < 0) {fprintf(stderr, "Filter avfilter_graph_parse_ptr failed\n");goto end;}/**（滤镜 6.5）：检查AVFilterGraph有效性*/if ((ret = avfilter_graph_config(filter_graph, NULL)) < 0) {fprintf(stderr, "Filter avfilter_graph_config failed\n");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;
}int init_filters() {const char *filter_spec;unsigned int i;int ret;filter_stm = (FilterStream *) (av_malloc_array(ifmt_ctx->nb_streams, sizeof(*filter_stm)));if (!filter_stm)return AVERROR(ENOMEM);//这里会根据音频和视频的stream_index创建对应的filter_stm组for (i = 0; i < ifmt_ctx->nb_streams; i++) {filter_stm[i].buffersrc_ctx = NULL;filter_stm[i].buffersink_ctx = NULL;filter_stm[i].filter_graph = NULL;if (!(ifmt_ctx->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_AUDIO|| ifmt_ctx->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO))continue;if (ifmt_ctx->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO)filter_spec = "null"; /* passthrough (dummy) filter for video */
//            filter_spec = "scale=iw/2:ih/2[in_tmp];[in_tmp]split=4[in_1][in_2][in_3][in_4];[in_1]pad=iw*2:ih*2[a];[a][in_2]overlay=w[b];[b][in_3]overlay=0:h[d];[d][in_4]overlay=w:h[out]"; /* passthrough (dummy) filter for video */elsefilter_spec = "anull"; /* passthrough (dummy) filter for audio */
//            filter_spec = "aecho=0.8:0.88:60:0.4"; /* passthrough (dummy) filter for audio */ret = init_filter(&filter_stm[i], ifmt_ctx->streams[i]->codec, ofmt_ctx->streams[i]->codec, filter_spec);if (ret)return ret;}return 0;
}int encode_write_frame(AVFrame *filt_frame, unsigned int stream_index) {int ret = -1;AVFrame *reasampling_frame;AVPacket *enc_pkt = av_packet_alloc();AVCodecContext *enc_ctx = ofmt_ctx->streams[stream_index]->codec;/* encode filtered frame */enc_pkt->data = NULL;enc_pkt->size = 0;av_init_packet(enc_pkt);if (!filt_frame) {//刷新缓存fprintf(stderr, "filt_frame is null , flush encode ?\n");avcodec_send_frame(enc_ctx, NULL);ret = 0;goto end;}//音频的这种情况需要重采样再进行输出if (stream_index == AVMEDIA_TYPE_AUDIO && filt_frame->nb_samples != enc_ctx->frame_size) {//输入的比输出的还小；参考官方例子：doc/examples/transcode_aac.cif (filt_frame->nb_samples < enc_ctx->frame_size) {/* Make the FIFO as large as it needs to be to hold both,* the old and the new samples. *//*if ((ret = av_audio_fifo_realloc(fifo, av_audio_fifo_size(fifo) + filt_frame->nb_samples)) < 0) {fprintf(stderr, "Could not reallocate FIFO\n");goto end;}*//* Store the new samples in the FIFO buffer. */int buf_size = av_audio_fifo_write(fifo, (void **) filt_frame->data,filt_frame->nb_samples);if (buf_size < filt_frame->nb_samples) {fprintf(stderr, "Could not write data to FIFO\n");ret = AVERROR_EXIT;goto end;}//这一次还不够转换int new_size = av_audio_fifo_size(fifo);if (new_size < enc_ctx->frame_size) {ret = 0;goto end;}}if (!(reasampling_frame = av_frame_alloc())) {fprintf(stderr, "Could not allocate oframe_a\n");ret = -1;goto end;}//把filt_frame参数复制给reasampling_frameif ((ret = av_frame_copy_props(reasampling_frame, filt_frame)) < 0) {fprintf(stderr, "copy filter frame failed\n");goto end;}//需要改变的reasampling_frame->format = enc_ctx->sample_fmt;reasampling_frame->channel_layout = enc_ctx->channel_layout;reasampling_frame->channels = enc_ctx->channels;reasampling_frame->sample_rate = enc_ctx->sample_rate;reasampling_frame->nb_samples = enc_ctx->frame_size;if ((ret = av_frame_get_buffer(reasampling_frame, 0)) < 0) {fprintf(stderr, "Error allocating an oframe_a buffer\n");goto end;}//这是处理fifo缓存数据if (filt_frame->nb_samples < enc_ctx->frame_size) {if (av_audio_fifo_read(fifo, (void **) reasampling_frame->data, reasampling_frame->nb_samples) <reasampling_frame->nb_samples) {fprintf(stderr, "Could not read data from FIFO\n");
//                    av_frame_free(&output_frame);ret = AVERROR_EXIT;goto end;}fprintf(stdout, "deal fifo\n");} else {/**（重采样 5.4）：重新采样*/if (swr_get_out_samples(swr_ctx, 0) >= enc_ctx->frame_size) {//当上次缓存足够时，取缓存if ((ret = swr_convert(swr_ctx, reasampling_frame->data, enc_ctx->frame_size, NULL, 0)) < 0) {fprintf(stderr, "resampling cache failed\n");goto end;}fprintf(stdout, "resampling cache\n");} else {//进行重采样if ((ret = swr_convert(swr_ctx, reasampling_frame->data, enc_ctx->frame_size,(const uint8_t **) filt_frame->data,filt_frame->nb_samples)) < 0) {fprintf(stderr, "resampling data failed\n");goto end;}}}//当解码的帧数与送去编码的帧数有差别时，我们必须更改pts和dts的值，否者封装时av_packet_rescale_ts（计算）pts和dts有重复，会出问题if(filt_frame->nb_samples != enc_ctx->frame_size){resample_pos += enc_ctx->frame_size;//编码前重新给pts和dts赋值reasampling_frame->pts = resample_pos;reasampling_frame->pkt_dts = resample_pos;}/**（编码 3.5）：把滤镜处理后的AVFrame送去编码*/ret = avcodec_send_frame(enc_ctx, reasampling_frame);} else {/**（编码 3.5）：把滤镜处理后的AVFrame送去编码*/ret = avcodec_send_frame(enc_ctx, filt_frame);}if (ret < 0) {fprintf(stderr, "Error sending the iframe to the encoder 2\n");goto end;}while (ret >= 0) {/**（编码 3.6）：从编码器中得到编码后数据，放入AVPacket中*/ret = avcodec_receive_packet(enc_ctx, enc_pkt);if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)//本次的ret只针对本循环，对外部为正常break;else if (ret < 0) {fprintf(stderr, "Error encoding iframe\n");goto end;}printf("write1 %s Packet. size:%5d\tdts:%5lld\tpts:%5lld\tduration:%5lld\tcur_dts:%5lld\n",stream_index == AVMEDIA_TYPE_AUDIO ? "a>>>>>" : "v-----",enc_pkt->size,  enc_pkt->dts, enc_pkt->pts, enc_pkt->duration,ofmt_ctx->streams[stream_index]->cur_dts);//设置pts等信息/* 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);enc_pkt->pos = -1;printf("write2 %s Packet. size:%5d\tdts:%5lld\tpts:%5lld\tduration:%5lld\tcur_dts:%5lld\n",stream_index == AVMEDIA_TYPE_AUDIO ? "a>>>>>" : "v-----",enc_pkt->size,  enc_pkt->dts, enc_pkt->pts, enc_pkt->duration,ofmt_ctx->streams[stream_index]->cur_dts);/**（封装 4.6）：将编码后的数据AVPacket进行封装，写入到文件*/if ((ret = av_interleaved_write_frame(ofmt_ctx, enc_pkt)) < 0) {fprintf(stderr, "Error muxer write to packet\n");goto end;}//擦除数据av_packet_unref(enc_pkt);}//当重采样缓存足够时，需要再次重采样，然后送去编码if (stream_index == AVMEDIA_TYPE_AUDIO && filt_frame->nb_samples != enc_ctx->frame_size) {if (swr_get_out_samples(swr_ctx, 0) >= enc_ctx->frame_size) {encode_write_frame(filt_frame, stream_index);}}ret = 0;end:av_packet_free(&enc_pkt);return ret;
}int filter_encode_write_frame(AVFrame *de_frame, unsigned int stream_index) {int ret;AVFrame *filt_frame = NULL;/**（滤镜 6.6）：将解码后的AVFrame送去filtergraph进行滤镜处理*/if ((ret = av_buffersrc_add_frame_flags(filter_stm[stream_index].buffersrc_ctx, de_frame,AV_BUFFERSRC_FLAG_KEEP_REF)) < 0) {fprintf(stderr, "Error while feeding the filtergraph\n");return ret;}/* pull filtered frames from the filtergraph */while (1) {if (!(filt_frame = av_frame_alloc())) {ret = AVERROR(ENOMEM);fprintf(stderr, "allow filter frame failed\n");goto end;}/**（滤镜 6.7）：得到滤镜处理后的数据*/ret = av_buffersink_get_frame(filter_stm[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;break;}filt_frame->pict_type = AV_PICTURE_TYPE_NONE;//然后把滤镜处理后的数据重新进行编码成你想要的格式，再封装输出if ((ret = encode_write_frame(filt_frame, stream_index)) < 0)break;}av_frame_free(&filt_frame);end:return ret;
}int main(int argc, char **argv) {
//    const char *in_filename = "source/Kobe.flv";
//    const char *out_filename = "output/Kobe.avi";
//    const char *in_filename = "source/lol.mp4";
//    const char *out_filename = "output/lol.avi";const char *in_filename = "source/心灵奇旅.mkv";const char *out_filename = "output/心灵奇旅.avi";remove(out_filename);int ret, i = -1;AVPacket *de_pkt = av_packet_alloc();AVFrame *de_frame = NULL;unsigned int stream_index;if ((ret = open_input_file(in_filename)) < 0)goto end;if ((ret = open_output_file(out_filename)) < 0)goto end;if ((ret = init_resampling()) < 0)goto end;if ((ret = init_filters()) < 0)goto end;if (!(fifo = av_audio_fifo_alloc(ofmt_ctx->streams[audio_index]->codec->sample_fmt,ofmt_ctx->streams[audio_index]->codec->channels,ofmt_ctx->streams[audio_index]->codec->frame_size * 2))) {fprintf(stderr, "Could not allocate FIFO\n");ret = AVERROR(ENOMEM);goto end;}while (1) {/**（解封装 1.3）：读取解封装后数据到AVPacket中*/if ((ret = av_read_frame(ifmt_ctx, de_pkt)) < 0)break;stream_index = de_pkt->stream_index;if (!(de_frame = av_frame_alloc())) {ret = AVERROR(ENOMEM);fprintf(stderr, "Error alloc frame\n");goto end;}//注意：av_packet_rescale_ts 在解码前重新计算pts、dts和duration的值，需要与编码时对应起来，防止视频和音频出现不同步// 注意传入的参数！AVStream和AVCodecContext的时间基。而我的AVCodecContext是通过生成的，并非原来的初始化时的。av_packet_rescale_ts(de_pkt,ifmt_ctx->streams[stream_index]->time_base,ifmt_ctx->streams[stream_index]->codec->time_base);/**（解码 2.5）：把AVPacket送去解码*//* read all the output frames (in general there may be any number of them */if ((ret = avcodec_send_packet(ifmt_ctx->streams[stream_index]->codec, de_pkt)) < 0) {fprintf(stderr, "Error submitting the packet to the decoder\n");goto end;}while (ret >= 0) {/**（解码 2.6）：从解码器获取解码后的数据到AVFrame*/ret = avcodec_receive_frame(ifmt_ctx->streams[stream_index]->codec, de_frame);if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {break;} else if (ret < 0) {fprintf(stderr, "Error during decoding\n");goto end;}de_frame->pts = de_frame->best_effort_timestamp;//这是解码后的裸数据，如果可以对其进行滤镜处理ret = filter_encode_write_frame(de_frame, stream_index);
//            ret = encode_write_frame(de_frame, stream_index);if (ret < 0)goto end;av_frame_unref(de_frame);}av_packet_unref(de_pkt);}/* flush the decoder and encoder*/for (i = 0; i < ifmt_ctx->nb_streams; i++) {avcodec_send_packet(ifmt_ctx->streams[i]->codec, NULL);avcodec_send_frame(ofmt_ctx->streams[i]->codec, NULL);}fprintf(stdout, "write the trailer\n");/**（封装 4.7）：写入文件尾*/av_write_trailer(ofmt_ctx);end:av_packet_free(&de_pkt);av_frame_free(&de_frame);for (i = 0; i < ifmt_ctx->nb_streams; i++) {avcodec_free_context(&ifmt_ctx->streams[i]->codec);if (ofmt_ctx && ofmt_ctx->nb_streams > i && ofmt_ctx->streams[i] && ofmt_ctx->streams[i]->codec)avcodec_free_context(&ofmt_ctx->streams[i]->codec);if (filter_stm && filter_stm[i].filter_graph)avfilter_graph_free(&filter_stm[i].filter_graph);}av_free(filter_stm);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 (fifo)av_audio_fifo_free(fifo);if (ret < 0)av_log(NULL, AV_LOG_ERROR, "Error occurred: %s\n", av_err2str(ret));return ret ? 1 : 0;
}

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