最简单的基于 FFmpeg 的音视频转码器（FLV 转 AVI）
参考雷霄骅博士的文章，链接：最简单的基于FFMPEG的转码程序
正文
本文介绍一个简单的基于 FFmpeg 的转码器。它可以将一种视频格式（包括封转格式和编码格式）转换为另一种视频格式。转码器在视音频编解码处理的程序中，属于一个比较复杂的东西。因为它结合了视频的解码和编码。一个视频播放器，一般只包含解码功能；一个视频编码工具，一般只包含编码功能；而一个视频转码器，则需要先对视频进行解码，然后再对视频进行编码，因而相当于解码器和编码器的结合。
下图例举了一个视频的转码流程。输入视频的封装格式是 FLV，视频编码标准是 H.264，音频编码标准是 AAC；输出视频的封装格式是 AVI，视频编码标准是 MPEG2，音频编码标准是 MP3。从流程中可以看出，首先从输入视频中分离出视频码流和音频压缩码流，然后分别将视频码流和音频码流进行解码，获取到非压缩的像素数据/音频采样数据，接着将非压缩的像素数据/音频采样数据重新进行编码，获得重新编码后的视频码流和音频码流，最后将视频码流和音频码流重新封装成一个文件。
本文介绍的视频转码器正是使用 FFmpeg 类库从编程的角度实现了上述流程。该例子是从 FFmpeg 的例子改编的，平台是 VC2015，类库版本是 2014.5.6。
流程图
下面附两张使用 FFmpeg 转码视频的流程图。图中使用浅绿色标出了视频的编码、解码函数。
简单介绍一下流程中各个函数的意义：
- open_input_file()：打开输入文件，并初始化相关的结构体。
- open_output_file()：打开输出文件，并初始化相关的结构体。
- init_filters()：初始化 AVFilter 相关的结构体。
- av_read_frame()：从输入文件中读取一个 AVPacket。
- avcodec_decode_video2()：解码一个视频 AVPacket（存储 H.264 等压缩码流数据）为 AVFrame（存储 YUV 等非压缩的像素数据）。
- avcodec_decode_audio4()：解码一个音频 AVPacket（存储 MP3 等压缩码流数据）为 AVFrame（存储 PCM 采样数据）。
- filter_encode_write_frame()：编码一个 AVFrame。
- flush_encoder()：输入文件读取完毕后，输出编码器中剩余的 AVPacket。
以上函数中 open_input_file()，open_output_file()，init_filters() 中的函数在其他文章中都有所叙述，在这里不再重复：
open_input_file() 可参考：100行代码实现最简单的基于FFMPEG+SDL的视频播放器（SDL1.x）
open_output_file() 可参考：最简单的基于FFMPEG的视频编码器（YUV编码为H.264）
init_filters()可参考：最简单的基于FFmpeg的AVfilter例子（水印叠加）
在这里介绍一下其中编码的函数 filter_encode_write_frame()。filter_encode_write_frame() 函数的流程如下图所示，它完成了视频/音频的编码功能。
PS：视频和音频的编码流程中除了编码函数 avcodec_encode_video2() 和 avcodec_encode_audio2() 不一样之外，其他部分几乎完全一样。
简单介绍一下 filter_encode_write_frame() 中各个函数的意义：
-
av_buffersrc_add_frame()：将解码后的 AVFrame 加入 Filtergraph。
-
av_buffersink_get_buffer_ref()：从 Filtergraph 中取一个 AVFrame。
-
avcodec_encode_video2()：编码一个视频 AVFrame 为 AVPacket。
-
avcodec_encode_audio2()：编码一个音频 AVFrame 为 AVPacket。
-
av_interleaved_write_frame()：将编码后的 AVPacket 写入文件。
源程序
// Simplest FFmpeg Transcoder.cpp : 定义控制台应用程序的入口点。
//
/**
* 最简单的基于 FFmpeg 的转码器
* Simplest FFmpeg Transcoder
*
* 源程序：
* 雷霄骅 Lei Xiaohua
* leixiaohua1020@126.com
* 中国传媒大学/数字电视技术
* Communication University of China / Digital TV Technology
* http://blog.youkuaiyun.com/leixiaohua1020
*
* 修改：
* 刘文晨 Liu Wenchen
* 812288728@qq.com
* 电子科技大学/电子信息
* University of Electronic Science and Technology of China / Electronic and Information Science
* https://blog.youkuaiyun.com/ProgramNovice
*
* 本程序实现了视频格式之间的转换。
* 是一个最简单的视频转码程序。
*/
#include "stdafx.h"
#include <stdio.h>
#include <stdlib.h>
// 解决报错：'fopen': This function or variable may be unsafe.Consider using fopen_s instead.
#pragma warning(disable:4996)
// 解决报错：无法解析的外部符号 __imp__fprintf，该符号在函数 _ShowError 中被引用
#pragma comment(lib, "legacy_stdio_definitions.lib")
extern "C"
{
// 解决报错：无法解析的外部符号 __imp____iob_func，该符号在函数 _ShowError 中被引用
FILE __iob_func[3] = { *stdin, *stdout, *stderr };
}
#define __STDC_CONSTANT_MACROS
#ifdef _WIN32
// Windows
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/avutil.h"
#include "libavutil/opt.h"
#include "libavutil/pixdesc.h"
};
#else
// Linux...
#ifdef __cplusplus
extern "C"
{
#endif
#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/avutil.h>
#include <libavutil/opt.h>
#include <libavutil/pixdesc.h>
#ifdef __cplusplus
};
#endif
#endif
static AVFormatContext *ifmt_ctx;
static AVFormatContext *ofmt_ctx;
typedef struct FilteringContext
{
AVFilterContext *buffersrc_ctx;
AVFilterContext *buffersink_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;
ret = avformat_open_input(&ifmt_ctx, filename, NULL, NULL);
if (ret < 0)
{
av_log(NULL, AV_LOG_ERROR, "Can't openinput file.\n");
return ret;
}
ret = avformat_find_stream_info(ifmt_ctx, NULL);
if (ret < 0)
{
av_log(NULL, AV_LOG_ERROR, "Can't 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;
}
}
}
// Print some input information
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, "Can't 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
|| dec_ctx->codec_type == AVMEDIA_TYPE_AUDIO)
{
// in this example, we choose transcoding to same codec
encoder = avcodec_find_encoder(dec_ctx->codec_id);
/* 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 formats
enc_ctx->pix_fmt = encoder->pix_fmts[0];
// video time_base can be set to whatever is handy andsupported by encoder
enc_ctx->time_base = dec_ctx->time_base;
}
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(enc_ctx->channel_layout);
// take first format from list of supported formats
enc_ctx->sample_fmt = encoder->sample_fmts[0];
AVRational time_base = { 1, enc_ctx->sample_rate };
enc_ctx->time_base = time_base;
}
// Third parameter can be used to pass settings to encoder
ret = avcodec_open2(enc_ctx, encoder, NULL);
if (ret < 0)
{
av_log(NULL, AV_LOG_ERROR, "Can't openvideo 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, can't proceed.\n", i);
return AVERROR_INVALIDDATA;
}
else
{
// if this stream must be remuxed
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;
}
// Print some output information
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, "Can't 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, "Can't 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, "Can't 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, "Can't 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%I64x",
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, "Can't 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, "Can't 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, "Can't 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, "Can't 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, "Can't 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;
}
ret = avfilter_graph_parse_ptr(filter_graph, filter_spec, &inputs, &outputs, NULL);
if (ret < 0)
goto end;
ret = avfilter_graph_config(filter_graph, NULL);
if (ret < 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)
{
// passthrough (dummy) filter for video
filter_spec = "null";
}
else
{
// passthrough (dummy) filter for audio
filter_spec = "anull";
}
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;
enc_pkt.dts = av_rescale_q_rnd(enc_pkt.dts,
ofmt_ctx->streams[stream_index]->codec->time_base,
ofmt_ctx->streams[stream_index]->time_base,
(AVRounding)(AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX));
enc_pkt.pts = av_rescale_q_rnd(enc_pkt.pts,
ofmt_ctx->streams[stream_index]->codec->time_base,
ofmt_ctx->streams[stream_index]->time_base,
(AVRounding)(AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX));
enc_pkt.duration = av_rescale_q(enc_pkt.duration,
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;
AVFrame *frame = NULL;
enum AVMediaType type;
unsigned int stream_index;
unsigned int i;
int got_frame;
int(*dec_func)(AVCodecContext *, AVFrame *, int *, const AVPacket*);
if (argc != 3)
{
av_log(NULL, AV_LOG_ERROR, "Usage: %s <input file> <output file>.\n", argv[0]);
return 1;
}
av_register_all();
avfilter_register_all();
// Open input file
ret = open_input_file(argv[1]);
if (ret < 0)
goto end;
// Open output file
ret = open_output_file(argv[2]);
if (ret < 0)
goto end;
// Init filters
ret = init_filters();
if (ret < 0)
goto end;
// Read all packets
while (1)
{
// Get a packet
ret = av_read_frame(ifmt_ctx, &packet);
if (ret < 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 and filter the frame.\n");
frame = av_frame_alloc();
if (!frame)
{
ret = AVERROR(ENOMEM);
break;
}
// 转换 DTS/PTS
packet.dts = av_rescale_q_rnd(packet.dts,
ifmt_ctx->streams[stream_index]->time_base,
ifmt_ctx->streams[stream_index]->codec->time_base,
(AVRounding)(AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX));
packet.pts = av_rescale_q_rnd(packet.pts,
ifmt_ctx->streams[stream_index]->time_base,
ifmt_ctx->streams[stream_index]->codec->time_base,
(AVRounding)(AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX));
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
packet.dts = av_rescale_q_rnd(packet.dts,
ifmt_ctx->streams[stream_index]->time_base,
ofmt_ctx->streams[stream_index]->time_base,
(AVRounding)(AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX));
packet.pts = av_rescale_q_rnd(packet.pts,
ifmt_ctx->streams[stream_index]->time_base,
ofmt_ctx->streams[stream_index]->time_base,
(AVRounding)(AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX));
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;
}
}
// Write file trailer
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_close(ofmt_ctx->pb);
avformat_free_context(ofmt_ctx);
if (ret < 0)
{
av_log(NULL, AV_LOG_ERROR, "Error occurred.\n");
return -1;
}
system("pause");
return 0;
}
结果
默认情况下运行程序，会将“cuc_ieschool.ts”转换为“cuc_ieschool.avi”。调试的时候，可以修改“配置属性->调试->命令参数”中的参数，即可改变转码的输入输出文件。
程序的运行结果如下：
输入文件：cuc_ieschool.ts
输出文件：cuc_ieschool.avi
工程文件下载
GitHub：UestcXiye / Simplest-FFmpeg-Transcoder
优快云：Simplest FFmpeg Transcoder.zip
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