本代码主要讲解了如何打开流媒体封装格式flv、mp4，获取音视频的信息，打印了前十帧音视频信息作为分析对象。
源代码：
#include
#include
int main(int argc, char **argv)
{
//打开网络流。这里如果只需要读取本地媒体文件，不需要用到网络功能，可以不用加上这一句
// avformat_network_init();
const char *default_filename = "believe.mp4";
char *in_filename = NULL;
if(argv[1] == NULL)
{
in_filename = default_filename;
}
else
{
in_filename = argv[1];
}
printf("in_filename = %s\n", in_filename);
//AVFormatContext是描述一个媒体文件或媒体流的构成和基本信息的结构体
AVFormatContext *ifmt_ctx = NULL; // 输入文件的demux
int videoindex = -1; // 视频索引
int audioindex = -1; // 音频索引
// 打开文件，主要是探测协议类型，如果是网络文件则创建网络链接
int ret = avformat_open_input(&ifmt_ctx, in_filename, NULL, NULL);
if (ret < 0) //如果打开媒体文件失败，打印失败原因
{
char buf[1024] = { 0 };
av_strerror(ret, buf, sizeof(buf) - 1);
printf("open %s failed:%s\n", in_filename, buf);
goto failed;
}
ret = avformat_find_stream_info(ifmt_ctx, NULL);
if (ret < 0) //如果打开媒体文件失败，打印失败原因
{
char buf[1024] = { 0 };
av_strerror(ret, buf, sizeof(buf) - 1);
printf("avformat_find_stream_info %s failed:%s\n", in_filename, buf);
goto failed;
}
//打开媒体文件成功
printf_s("\n==== av_dump_format in_filename:%s ===\n", in_filename);
av_dump_format(ifmt_ctx, 0, in_filename, 0);
printf_s("\n==== av_dump_format finish =======\n\n");
// url: 调用avformat_open_input读取到的媒体文件的路径/名字
printf("media name:%s\n", ifmt_ctx->url);
// nb_streams: nb_streams媒体流数量
printf("stream number:%d\n", ifmt_ctx->nb_streams);
// bit_rate: 媒体文件的码率,单位为bps
printf("media average ratio:%lldkbps\n",(int64_t)(ifmt_ctx->bit_rate/1024));
// 时间
int total_seconds, hour, minute, second;
// duration: 媒体文件时长，单位微妙
total_seconds = (ifmt_ctx->duration) / AV_TIME_BASE; // 1000us = 1ms, 1000ms = 1秒
hour = total_seconds / 3600;
minute = (total_seconds % 3600) / 60;
second = (total_seconds % 60);
//通过上述运算，可以得到媒体文件的总时长
printf("total duration: %02d:%02d:%02d\n", hour, minute, second);
printf("\n");
/*
* 老版本通过遍历的方式读取媒体文件视频和音频的信息
* 新版本的FFmpeg新增加了函数av_find_best_stream，也可以取得同样的效果
*/
for (uint32_t i = 0; i < ifmt_ctx->nb_streams; i++)
{
AVStream *in_stream = ifmt_ctx->streams[i];// 音频流、视频流、字幕流
//如果是音频流，则打印音频的信息
if (AVMEDIA_TYPE_AUDIO == in_stream->codecpar->codec_type)
{
printf("----- Audio info:\n");
// index: 每个流成分在ffmpeg解复用分析后都有唯一的index作为标识
printf("index:%d\n", in_stream->index);
// sample_rate: 音频编解码器的采样率，单位为Hz
printf("samplerate:%dHz\n", in_stream->codecpar->sample_rate);
// codecpar->format: 音频采样格式
if (AV_SAMPLE_FMT_FLTP == in_stream->codecpar->format)
{
printf("sampleformat:AV_SAMPLE_FMT_FLTP\n");
}
else if (AV_SAMPLE_FMT_S16P == in_stream->codecpar->format)
{
printf("sampleformat:AV_SAMPLE_FMT_S16P\n");
}
// channels: 音频信道数目
printf("channel number:%d\n", in_stream->codecpar->channels);
// codec_id: 音频压缩编码格式
if (AV_CODEC_ID_AAC == in_stream->codecpar->codec_id)
{
printf("audio codec:AAC\n");
}
else if (AV_CODEC_ID_MP3 == in_stream->codecpar->codec_id)
{
printf("audio codec:MP3\n");
}
else
{
printf("audio codec_id:%d\n", in_stream->codecpar->codec_id);
}
// 音频总时长，单位为秒。注意如果把单位放大为毫秒或者微妙，音频总时长跟视频总时长不一定相等的
if(in_stream->duration != AV_NOPTS_VALUE)
{
int duration_audio = (in_stream->duration) * av_q2d(in_stream->time_base);
//将音频总时长转换为时分秒的格式打印到控制台上
printf("audio duration: %02d:%02d:%02d\n",
duration_audio / 3600, (duration_audio % 3600) / 60, (duration_audio % 60));
}
else
{
printf("audio duration unknown");
}
printf("\n");
audioindex = i; // 获取音频的索引
}
else if (AVMEDIA_TYPE_VIDEO == in_stream->codecpar->codec_type) //如果是视频流，则打印视频的信息
{
printf("----- Video info:\n");
printf("index:%d\n", in_stream->index);
// avg_frame_rate: 视频帧率,单位为fps，表示每秒出现多少帧
printf("fps:%lffps\n", av_q2d(in_stream->avg_frame_rate));
if (AV_CODEC_ID_MPEG4 == in_stream->codecpar->codec_id) //视频压缩编码格式
{
printf("video codec:MPEG4\n");
}
else if (AV_CODEC_ID_H264 == in_stream->codecpar->codec_id) //视频压缩编码格式
{
printf("video codec:H264\n");
}
else
{
printf("video codec_id:%d\n", in_stream->codecpar->codec_id);
}
// 视频帧宽度和帧高度
printf("width:%d height:%d\n", in_stream->codecpar->width,
in_stream->codecpar->height);
//视频总时长，单位为秒。注意如果把单位放大为毫秒或者微妙，音频总时长跟视频总时长不一定相等的
if(in_stream->duration != AV_NOPTS_VALUE)
{
int duration_video = (in_stream->duration) * av_q2d(in_stream->time_base);
printf("video duration: %02d:%02d:%02d\n",
duration_video / 3600,
(duration_video % 3600) / 60,
(duration_video % 60)); //将视频总时长转换为时分秒的格式打印到控制台上
}
else
{
printf("video duration unknown");
}
printf("\n");
videoindex = i;
}
}
AVPacket *pkt = av_packet_alloc();
int pkt_count = 0;
int print_max_count = 10;
printf("\n-----av_read_frame start\n");
while (1)
{
ret = av_read_frame(ifmt_ctx, pkt);
if (ret < 0)
{
printf("av_read_frame end\n");
break;
}
if(pkt_count++ < print_max_count)
{
if (pkt->stream_index == audioindex)
{
printf("audio pts: %lld\n", pkt->pts);
printf("audio dts: %lld\n", pkt->dts);
printf("audio size: %d\n", pkt->size);
printf("audio pos: %lld\n", pkt->pos);
printf("audio duration: %lf\n\n",
pkt->duration * av_q2d(ifmt_ctx->streams[audioindex]->time_base));
}
else if (pkt->stream_index == videoindex)
{
printf("video pts: %lld\n", pkt->pts);
printf("video dts: %lld\n", pkt->dts);
printf("video size: %d\n", pkt->size);
printf("video pos: %lld\n", pkt->pos);
printf("video duration: %lf\n\n",
pkt->duration * av_q2d(ifmt_ctx->streams[videoindex]->time_base));
}
else
{
printf("unknown stream_index:\n", pkt->stream_index);
}
}
av_packet_unref(pkt);
}
if(pkt)
av_packet_free(&pkt);
failed:
if(ifmt_ctx)
avformat_close_input(&ifmt_ctx);
getchar(); //加上这一句，防止程序打印完信息马上退出
return 0;
}
输出结果：
in_filename = believe.flv
==== av_dump_format in_filename:believe.flv ===
Input #0, flv, from 'believe.flv':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
comment : www.ieway.cn
encoder : Lavf58.29.100
Duration: 00:03:42.53, start: 0.000000, bitrate: 286 kb/s
Stream #0:0: Video: h264 (Constrained Baseline), yuv420p(progressive), 1920x1080, 150 kb/s, 14.46 fps, 15 tbr, 1k tbn, 30 tbc
Stream #0:1: Audio: aac (LC), 48000 Hz, stereo, fltp, 128 kb/s
==== av_dump_format finish =======
media name:believe.flv
stream number:2
media average ratio:279kbps
total duration: 00:03:42
----- Video info:
index:0
fps:14.464286fps
video codec:H264
width:1920 height:1080
video duration unknown
----- Audio info:
index:1
samplerate:48000Hz
sampleformat:AV_SAMPLE_FMT_FLTP
channel number:2
audio codec:AAC
audio duration unknown
-----av_read_frame start
audio pts: 0
audio dts: 0
audio size: 341
audio pos: 502
audio duration: 0.021000
video pts: 14
video dts: 14
video size: 66736
video pos: 860
video duration: 0.066000
audio pts: 21
audio dts: 21
audio size: 341
audio pos: 67616
audio duration: 0.021000
audio pts: 43
audio dts: 43
audio size: 342
audio pos: 67974
audio duration: 0.021000
audio pts: 64
audio dts: 64
audio size: 341
audio pos: 68333
audio duration: 0.021000
video pts: 81
video dts: 81
video size: 580
video pos: 68691
video duration: 0.066000
audio pts: 85
audio dts: 85
audio size: 341
audio pos: 69291
audio duration: 0.021000
audio pts: 107
audio dts: 107
audio size: 342
audio pos: 69649
audio duration: 0.021000
audio pts: 128
audio dts: 128
audio size: 341
audio pos: 70008
audio duration: 0.021000
video pts: 147
video dts: 147
video size: 11289
video pos: 70366
video duration: 0.066000
av_read_frame end