文章目录
- 一、通过此文可以得到什么
- 二、实现思路
- 三、实现效果
- 四、实现源代码
一、通过此文可以得到什么
通过此练习：
- 1、知道了如何计算一个音频和视频的播放时间；
- 2、知道了音视频解码的思路的大体流程，之后无非就是在这个流程上进行扩充细节；
- 3、知道了如何通过C语言或者C 编程语言结合ffmpeg拿到一些音视频的关键信息，例如：帧率等；
二、实现思路
三、实现效果
代码语言：javascript复制zhenghui@zh-pc:/data/project/VSCProject/ffmpegStudy$ make
make all
make[1]: 进入目录“/data/project/VSCProject/ffmpegStudy/src”
Compiling main.cpp to main.o ..
cp hello /data/project/VSCProject/ffmpegStudy/src/../
# make 【hello】 finish !!!
make[1]: 离开目录“/data/project/VSCProject/ffmpegStudy/src”
zhenghui@zh-pc:/data/project/VSCProject/ffmpegStudy$
zhenghui@zh-pc:/data/project/VSCProject/ffmpegStudy$ ./hello
Hello World !
decode video fileName=/home/zhenghui/视频/1080P.mp4
[NULL @ 0x5654cc332d80] Opening '/home/zhenghui/视频/1080P.mp4' for reading
[file @ 0x5654cc333380] Setting default whitelist 'file,crypto,data'
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x5654cc332d80] Format mov,mp4,m4a,3gp,3g2,mj2 probed with size=2048 and score=100
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x5654cc332d80] ISO: File Type Major Brand: isom
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x5654cc332d80] Unknown dref type 0x206c7275 size 12
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x5654cc332d80] Processing st: 0, edit list 0 - media time: 1072, duration: 3621888
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x5654cc332d80] Offset DTS by 1072 to make first pts zero.
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x5654cc332d80] Setting codecpar->delay to 2 for stream st: 0
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x5654cc332d80] Unknown dref type 0x206c7275 size 12
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x5654cc332d80] Processing st: 1, edit list 0 - media time: 0, duration: 9990149
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x5654cc332d80] rfps: 29.916667 0.006250
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x5654cc332d80] rfps: 30.000000 0.000066
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x5654cc332d80] rfps: 60.000000 0.000265
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x5654cc332d80] rfps: 120.000000 0.001061
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x5654cc332d80] rfps: 240.000000 0.004244
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x5654cc332d80] rfps: 29.970030 0.000868
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x5654cc332d80] rfps: 59.940060 0.003473
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x5654cc332d80] Before avformat_find_stream_info() pos: 87425182 bytes read:315205 seeks:1 nb_streams:2
[h264 @ 0x5654cc3340c0] nal_unit_type: 7(SPS), nal_ref_idc: 3
[h264 @ 0x5654cc3340c0] nal_unit_type: 8(PPS), nal_ref_idc: 3
[h264 @ 0x5654cc3340c0] nal_unit_type: 7(SPS), nal_ref_idc: 3
[h264 @ 0x5654cc3340c0] nal_unit_type: 8(PPS), nal_ref_idc: 3
[h264 @ 0x5654cc3340c0] nal_unit_type: 6(SEI), nal_ref_idc: 0
[h264 @ 0x5654cc3340c0] nal_unit_type: 5(IDR), nal_ref_idc: 3
[h264 @ 0x5654cc3340c0] Format yuv420p chosen by get_format().
[h264 @ 0x5654cc3340c0] Reinit context to 1920x1088, pix_fmt: yuv420p
[h264 @ 0x5654cc3340c0] no picture
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x5654cc332d80] All info found
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x5654cc332d80] After avformat_find_stream_info() pos: 53231 bytes read:393067 seeks:2 frames:4
video_index=0
audio_index=1
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/home/zhenghui/视频/1080P.mp4':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
encoder : Lavf58.29.100
description : Packed by Bilibili XCoder v2.0.2
Duration: 00:03:46.53, start: 0.000000, bitrate: 3087 kb/s
Stream #0:0[0x1](und), 3, 1/16000: Video: h264 (High), 1 reference frame (avc1 / 0x31637661), yuv420p(progressive, left), 1920x1080 (1920x1088) [SAR 1:1 DAR 16:9], 0/1, 2951 kb/s, 30 fps, 30 tbr, 16k tbn (default)
Metadata:
handler_name : VideoHandler
vendor_id : [0][0][0][0]
Stream #0:1[0x2](und), 1, 1/44100: Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 128 kb/s (default)
Metadata:
handler_name : SoundHandler
vendor_id : [0][0][0][0]
media name =/home/zhenghui/视频/1080P.mp4
stream number: 2
media average ratio: 3015 kbps
media total time: 0:3:46
######## Video info: ########
stream index : 0
fps:29.999914 fps
video codec : H264
video_time : 00:03:46
######## Audio info: ########
stream index : 1
stream sample_rate : 44100 Hz
stream format : AV_SAMPLE_FMT_FLTP
channels number:2
audio codec:AAC
audio_time : 00:03:46
[AVIOContext @ 0x5654cc33b7c0] Statistics: 393067 bytes read, 2 seeks
zhenghui@zh-pc:/data/project/VSCProject/ffmpegStudy$ 四、实现源代码
0声Darren哥牛
代码语言：javascript复制#include <iostream>
#include <stdio.h>
#ifdef __cplusplus //表示是一个c 程序
extern "C"{
#endif
#include <libavdevice/avdevice.h>
#include <libavutil/frame.h>
#include <libavutil/imgutils.h>
#include <libavutil/log.h>
#include <libswscale/swscale.h>
#include <libavformat/avformat.h>
#include <libavcodec/avcodec.h>
#ifdef __cplusplus
}
#endif
//g -I ../include/ hello_world.cpp -o hello_world -L../lib/ -lavcodec -lavdevice -lavfilter -lavformat -lavutil
void decode()
{
char *fileName = "/home/zhenghui/视频/1080P.mp4";
printf("decode video fileName=%s n",fileName);
int ret = 0;
// 1、分配解复用器上下文
AVFormatContext *ctx = NULL;
ctx = avformat_alloc_context();
// 2、根据url打开本地文件或网络流
ret = avformat_open_input(&ctx,fileName,NULL,NULL);
if(ret < 0)
{
printf("打开%s失败 ! n",fileName);
return;
}
// 3、读取媒体的部分数据包，获取码流信息
ret = avformat_find_stream_info(ctx,NULL);
if(ret < 0){
printf("获取码流信息失败 !n");
return;
}
// 3、获取音频流和视频流的索引
int video_index = -1;
int audio_index = -1;
video_index = av_find_best_stream(ctx,AVMEDIA_TYPE_VIDEO,-1,-1,NULL,0);
printf("video_index=%d n",video_index);
audio_index = av_find_best_stream(ctx,AVMEDIA_TYPE_AUDIO,-1,-1,NULL,0);
printf("audio_index=%d n",audio_index);
// 打印流信息
av_dump_format(ctx,0,fileName,0);
//打印媒体文件url
printf("media name =%s n",ctx->url);
//打印流数量
printf("stream number: %d n",ctx->nb_streams);
//打印码率
printf("media average ratio: %lld kbpsn",(int64_t)(ctx->bit_rate/1024));
//打印时长
int total_seconds,hour,minute,second;
//ctx->duration的单位是微妙，先转换成秒，再进行转换成其他的时间单位就比较简单了
total_seconds = (ctx->duration) / AV_TIME_BASE;
hour = total_seconds / 3600;
minute = (total_seconds % 3600) /60;
second = (total_seconds % 60);
// 文件总时长
printf("media total time: %d:%d:%d n",hour,minute,second);
//老版本查找流索引
for(int i = 0;i < ctx->nb_streams;i ){
AVStream *av_stream = ctx->streams[i];
//判断流是什么类型
//视频流
if( AVMEDIA_TYPE_VIDEO == av_stream->codecpar->codec_type)
{
printf("######## Video info: ######## n");
// 流索引
printf("stream index : %d n",av_stream->index);
//帧率
printf("fps:%lf fpsn",av_q2d(av_stream->avg_frame_rate));
if(AV_CODEC_ID_MPEG4 == av_stream->codecpar->codec_id)
{
printf("video codec : MPEG4 n");
}
else if(AV_CODEC_ID_H264 == av_stream->codecpar->codec_id)
{
printf("video codec : H264 n");
}else
{
printf("video codec other value=%d n", av_stream->codecpar->codec_id);
}
//获取视频总时长
if(AV_NOPTS_VALUE != av_stream->duration)
{
int video_time =av_stream->duration * av_q2d(av_stream->time_base);
printf("video_time : d:d:dn" ,
(video_time / 3600),
(video_time % 3600) / 60,
(video_time % 60)
);
}
else{
printf("audio duration unknown ! n");
}
}
//音频流
else if(AVMEDIA_TYPE_AUDIO == av_stream->codecpar->codec_type)
{
printf("######## Audio info: ######## n");
// 流索引
printf("stream index : %d n",av_stream->index);
// 音频编解码器的采样率 单位Hz
printf("stream sample_rate : %d Hz n",av_stream->codecpar->sample_rate);
//音频采样格式
if(AV_SAMPLE_FMT_FLTP == av_stream->codecpar->format)
{
printf("stream format : AV_SAMPLE_FMT_FLTP n");
}
else if(AV_SAMPLE_FMT_S16P == av_stream->codecpar->format)
{
printf("stream format : AV_SAMPLE_FMT_S16P n");
}else{
printf("stream format : other； value=%d n",av_stream->codecpar->format);
}
// 音频信道数目
printf("channels number:%d n",av_stream->codecpar->channels);
//音频压缩编码格式
if(AV_CODEC_ID_AAC == av_stream->codecpar->codec_id)
{
printf("audio codec:AAC n");
}else if(AV_CODEC_ID_MP3 == av_stream->codecpar->codec_id)
{
printf("audio codec:MP3 n");
}else{
printf("audio codec : other； value=%d n",av_stream->codecpar->codec_id);
}
//获取视频总时长
if(AV_NOPTS_VALUE != av_stream->duration)
{
int audio_time =av_stream->duration * av_q2d(av_stream->time_base);
printf("audio_time : d:d:dn" ,
(audio_time / 3600),
(audio_time % 3600) / 60,
(audio_time % 60)
);
}
else{
printf("audio duration unknown ! n");
}
audio_index = i;
}
}
if(ctx)
avformat_close_input(&ctx);
}
int main() {
// 设置控制台输出级别
av_log_set_level(AV_LOG_DEBUG);
// // 打印输出字符串Hello World ！
av_log(NULL, AV_LOG_DEBUG, "%s", "Hello World !n");
decode();
return 0;
}
