视频解码
// ffmpegdemo.cpp : 定义控制台应用程序的入口点。
//
#include "stdafx.h"
#include
#define __STDC_CONSTANT_MACROS
#ifdef _WIN32
//Windows
extern "C"
{
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
#include "libswscale/swscale.h"
#include "libavutil/imgutils.h"
};
#else
//Linux...
#ifdef __cplusplus
extern "C"
{
#endif
#include
#include
#include
#include
#ifdef __cplusplus
};
#endif
#endif
int main()
{
//文件格式上下文
AVFormatContext *pFormatCtx;
int i = 0, videoindex;
AVCodecContext *pCodecCtx;
AVCodec *pCodec;
AVFrame *pFrame, *pFrameYUV;
unsigned char *out_buffer;
AVPacket *packet;
int y_size;
int ret, got_picture;
struct SwsContext *img_convert_ctx;
char filepath[] = "input.mkv";
FILE *fp_yuv = fopen("output.yuv", "wb+");
av_register_all();
avformat_network_init();
pFormatCtx = avformat_alloc_context();
if (avformat_open_input(&pFormatCtx, filepath, NULL, NULL) != 0)
{
printf("Couldn't open input stream.\n");
return -1;
}
//读取一部分视音频数据并且获得一些相关的信息
if (avformat_find_stream_info(pFormatCtx, NULL) < 0)
{
printf("Couldn't find stream information.\n");
return -1;
}
//查找视频编码索引
videoindex = -1;
for (i = 0; i < pFormatCtx->nb_streams; i++)
{
if (pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO)
{
videoindex = i;
break;
}
}
if (videoindex == -1)
{
printf("Didn't find a video stream.\n");
return -1;
}
//编解码上下文
pCodecCtx = pFormatCtx->streams[videoindex]->codec;
//查找解码器
pCodec = avcodec_find_decoder(pCodecCtx->codec_id);
if (pCodec == NULL)
{
printf("Codec not found.\n");
return -1;
}
//打开解码器
if (avcodec_open2(pCodecCtx, pCodec, NULL) < 0)
{
printf("Could not open codec.\n");
return -1;
}
//申请AVFrame,用于原始视频
pFrame = av_frame_alloc();
//申请AVFrame,用于yuv视频
pFrameYUV = av_frame_alloc();
//分配内存,用于图像格式转换
out_buffer = (unsigned char *)av_malloc(av_image_get_buffer_size(AV_PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height, 1));
av_image_fill_arrays(pFrameYUV->data, pFrameYUV->linesize, out_buffer,AV_PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height, 1);
packet = (AVPacket *)av_malloc(sizeof(AVPacket));
//Output Info-----------------------------
printf("--------------- File Information ----------------\n");
//手工调试函数,输出tbn、tbc、tbr、PAR、DAR的含义
av_dump_format(pFormatCtx, 0, filepath, 0);
printf("-------------------------------------------------\n");
//申请转换上下文
img_convert_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt,
pCodecCtx->width, pCodecCtx->height, AV_PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL);
//读取数据
while (av_read_frame(pFormatCtx, packet) >= 0)
{
if (packet->stream_index == videoindex)
{
ret = avcodec_decode_video2(pCodecCtx, pFrame, &got_picture, packet);
if (ret < 0)
{
printf("Decode Error.\n");
return -1;
}
if (got_picture >= 1)
{
//成功解码一帧
sws_scale(img_convert_ctx, (const unsigned char* const*)pFrame->data, pFrame->linesize, 0, pCodecCtx->height,
pFrameYUV->data, pFrameYUV->linesize);//转换图像格式
y_size = pCodecCtx->width*pCodecCtx->height;
fwrite(pFrameYUV->data[0], 1, y_size, fp_yuv); //Y
fwrite(pFrameYUV->data[1], 1, y_size / 4, fp_yuv); //U
fwrite(pFrameYUV->data[2], 1, y_size / 4, fp_yuv); //V
printf("Succeed to decode 1 frame!\n");
}
else
{
//未解码到一帧,可能时结尾B帧或延迟帧,在后面做flush decoder处理
}
}
av_free_packet(packet);
}
//flush decoder
//FIX: Flush Frames remained in Codec
while (true)
{
if (!(pCodec->capabilities & CODEC_CAP_DELAY))
return 0;
ret = avcodec_decode_video2(pCodecCtx, pFrame, &got_picture, packet);
if (ret < 0)
{
break;
}
if (!got_picture)
{
break;
}
sws_scale(img_convert_ctx, (const unsigned char* const*)pFrame->data, pFrame->linesize, 0, pCodecCtx->height,
pFrameYUV->data, pFrameYUV->linesize);
int y_size = pCodecCtx->width*pCodecCtx->height;
fwrite(pFrameYUV->data[0], 1, y_size, fp_yuv); //Y
fwrite(pFrameYUV->data[1], 1, y_size / 4, fp_yuv); //U
fwrite(pFrameYUV->data[2], 1, y_size / 4, fp_yuv); //V
printf("Flush Decoder: Succeed to decode 1 frame!\n");
}
sws_freeContext(img_convert_ctx);
av_frame_free(&pFrameYUV);
av_frame_free(&pFrame);
avcodec_close(pCodecCtx);
avformat_close_input(&pFormatCtx);
fclose(fp_yuv);
return 0;
}
视频编码
// ffmpegdemo.cpp : 定义控制台应用程序的入口点。
//
#include "stdafx.h"
#include
#define __STDC_CONSTANT_MACROS
#ifdef _WIN32
//Windows
extern "C"
{
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
#include "libswscale/swscale.h"
#include "libavutil/imgutils.h"
};
#else
//Linux...
#ifdef __cplusplus
extern "C"
{
#endif
#include
#include
#include
#include
#ifdef __cplusplus
};
#endif
#endif
int flush_encoder(AVFormatContext *fmt_ctx, unsigned int stream_index)
{
int ret;
int got_frame;
AVPacket enc_pkt;
if (!(fmt_ctx->streams[stream_index]->codec->codec->capabilities &CODEC_CAP_DELAY))
{
return 0;
}
while (true)
{
enc_pkt.data = NULL;
enc_pkt.size = 0;
av_init_packet(&enc_pkt);
ret = avcodec_encode_video2(fmt_ctx->streams[stream_index]->codec, &enc_pkt,NULL, &got_frame);
av_frame_free(NULL);
if (ret < 0)
{
break;
}
if (!got_frame)
{
ret = 0;
break;
}
printf("Flush Encoder: Succeed to encode 1 frame!\tsize:%5d\n", enc_pkt.size);
/* mux encoded frame */
ret = av_write_frame(fmt_ctx, &enc_pkt);
if (ret < 0)
{
break;
}
}
return ret;
}
int main()
{
AVFormatContext* pFormatCtx;
AVOutputFormat* pOutputFmt;
AVStream* video_st;
AVCodecContext* pCodecCtx;
AVCodec* pCodec;
AVPacket pkt;
uint8_t* picture_buf;
AVFrame* pFrame;
int picture_size;
int y_size;
int framecnt = 0;
int in_w = 640, in_h = 272; //视频图像宽高
const char* out_file = "output.h264";
int i, j;
int num;
int index_y, index_u, index_v;
uint8_t *y_, *u_, *v_, *in;
int got_picture = 0;
int ret;
av_register_all();
//alloc avformat context
pFormatCtx = avformat_alloc_context();
//猜测类型,返回输出类型。
pOutputFmt = av_guess_format(NULL, out_file, NULL);
pFormatCtx->oformat = pOutputFmt;
//打开FFmpeg的输入输出文件,成功之后创建的AVIOContext结构体。
if (avio_open2(&pFormatCtx->pb, out_file, AVIO_FLAG_READ_WRITE,NULL,NULL) < 0)
{
//Failed to open output file
return -1;
}
//除了以下方法,另外还可以使用avcodec_find_encoder_by_name()来获取AVCodec
pCodec = avcodec_find_encoder(pOutputFmt->video_codec);//获取编码器
if (!pCodec)
{
//cannot find encoder
return -1;
}
pCodecCtx = avcodec_alloc_context3(pCodec);//申请AVCodecContext,并初始化。
if (!pCodecCtx)
{
//failed get AVCodecContext
return -1;
}
FILE * in_file = fopen("640-272.yuv", "rb"); //打开原始yuv数据文件
/* 创建输出码流的AVStream */
video_st = avformat_new_stream(pFormatCtx, 0);
video_st->time_base.num = 1;
video_st->time_base.den = 25;
if (video_st == NULL)
{
return -1;
}
//Param that must set
pCodecCtx = video_st->codec;
//pCodecCtx->codec_id =AV_CODEC_ID_HEVC; //H265
pCodecCtx->codec_id = AV_CODEC_ID_H264;
pCodecCtx->codec_type = AVMEDIA_TYPE_VIDEO;
pCodecCtx->pix_fmt = AV_PIX_FMT_YUV420P;
pCodecCtx->width = in_w;
pCodecCtx->height = in_h;
pCodecCtx->b_frame_strategy = true;
/*
码率
bit_rate/-bt tolerance 设置视频码率容忍度kbit/s (固定误差)
rc_max_rate/-maxrate bitrate设置最大视频码率容忍度 (可变误差)
rc_min_rate/-minrate bitreate 设置最小视频码率容忍度(可变误差)
rc_buffer_size/-bufsize size 设置码率控制缓冲区大小
如何设置固定码率编码 ?
bit_rate是平均码率,不一定能控制住
c->bit_rate = 400000;
c->rc_max_rate = 400000;
c->rc_min_rate = 400000;
提示 [libx264 @ 00c70be0] VBV maxrate specified, but no bufsize, ignored
再设置 c->rc_buffer_size = 200000; 即可。如此控制后编码质量明显差了。
*/
pCodecCtx->bit_rate = 400000; //采样码率越大,目标文件越大
//pCodecCtx->bit_rate_tolerance = 8000000; // 码率误差,允许的误差越大,视频越小
//两个I帧之间的间隔
pCodecCtx->gop_size = 15;
//编码帧率,每秒多少帧。下面表示1秒25帧
pCodecCtx->time_base.num = 1;
pCodecCtx->time_base.den = 25;
//最小的量化因子
pCodecCtx->qmin = 10;
//最大的量化因子
pCodecCtx->qmax = 30;
//最大B帧数
pCodecCtx->max_b_frames = 3;
// Set Option
AVDictionary *param = 0;
//H.264
if (pCodecCtx->codec_id == AV_CODEC_ID_H264)
{
/*
preset的参数主要调节编码速度和质量的平衡,有ultrafast、superfast、veryfast、faster、fast、medium、slow、slower、veryslow、placebo这10个选项,从快到慢。
*/
av_dict_set(¶m, "preset", "fast", 0);
/*
tune的参数主要配合视频类型和视觉优化的参数。
tune的值有: film: 电影、真人类型;
animation: 动画;
grain: 需要保留大量的grain时用;
stillimage: 静态图像编码时使用;
psnr: 为提高psnr做了优化的参数;
ssim: 为提高ssim做了优化的参数;
fastdecode: 可以快速解码的参数;
zerolatency:零延迟,用在需要非常低的延迟的情况下,比如电视电话会议的编码。
*/
av_dict_set(¶m, "tune", "zerolatency", 0);
/*
画质,分别是baseline, extended, main, high
1、Baseline Profile:基本画质。支持I/P 帧,只支持无交错(Progressive)和CAVLC;
2、Extended profile:进阶画质。支持I/P/B/SP/SI 帧,只支持无交错(Progressive)和CAVLC;(用的少)
3、Main profile:主流画质。提供I/P/B 帧,支持无交错(Progressive)和交错(Interlaced), 也支持CAVLC 和CABAC 的支持;
4、High profile:高级画质。在main Profile 的基础上增加了8x8内部预测、自定义量化、 无损视频编码和更多的YUV 格式;
H.264 Baseline profile、Extended profile和Main profile都是针对8位样本数据、4:2:0格式(YUV)的视频序列。在相同配置情况下,
High profile(HP)可以比Main profile(MP)降低10%的码率。 根据应用领域的不同,Baseline profile多应用于实时通信领域,
Main profile多应用于流媒体领域,High profile则多应用于广电和存储领域。
*/
//av_dict_set(¶m, "profile", "main", 0);
}
else if (pCodecCtx->codec_id == AV_CODEC_ID_H265 || pCodecCtx->codec_id == AV_CODEC_ID_HEVC)
{
av_dict_set(¶m, "preset", "fast", 0);
av_dict_set(¶m, "tune", "zerolatency", 0);
}
//Output Info-----------------------------
printf("--------------- out_file Information ----------------\n");
//手工调试函数,输出tbn、tbc、tbr、PAR、DAR的含义
av_dump_format(pFormatCtx, 0, out_file, 1); //最后一个参数,如果是输出文件时,该值为1;如果是输入文件时,该值为0
printf("-----------------------------------------------------\n");
/* 查找编码器 */
pCodec = avcodec_find_encoder(pCodecCtx->codec_id);
if (!pCodec)
{
printf("Can not find encoder! \n");
return -1;
}
/* 打开编码器 */
if (avcodec_open2(pCodecCtx, pCodec,¶m) < 0)
{
printf("Failed to open encoder! \n");
return -1;
}
pFrame = av_frame_alloc();
picture_size = avpicture_get_size(pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height);
picture_buf = (uint8_t *)av_malloc(picture_size);
avpicture_fill((AVPicture *)pFrame, picture_buf, pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height);
//Write File Header
/* 写文件头(对于某些没有文件头的封装格式,不需要此函数。比如说MPEG2TS) */
avformat_write_header(pFormatCtx, NULL);
/* Allocate the payload of a packet and initialize its fields with default values. */
av_new_packet(&pkt, picture_size);
j = 1;
y_size = pCodecCtx->width * pCodecCtx->height;
unsigned int uiReadSize = 0;
while (true)
{
//Read raw YUV data
if (feof(in_file)) //文件结束
{
break;
}
else
{
uiReadSize = fread(picture_buf, 1, y_size * 3 / 2, in_file);
if (uiReadSize <= 0)
{
printf("Failed to read raw data! \n");
break;
}
else if (uiReadSize < y_size * 3 / 2)
{
//读取数据不满足一帧YUV数据,表示数据读取完
break;
}
}
pFrame->data[0] = picture_buf; // Y
pFrame->data[1] = picture_buf + y_size; // U
pFrame->data[2] = picture_buf + y_size * 5 / 4; // V
//PTS
pFrame->pts = j*(video_st->time_base.den) / ((video_st->time_base.num) * 25);
//Encode
/* 编码一帧视频。即将AVFrame(存储YUV像素数据)编码为AVPacket(存储H.264等格式的码流数据) */
int ret = avcodec_encode_video2(pCodecCtx, &pkt, pFrame, &got_picture);
if (ret < 0)
{
printf("Failed to encode! \n");
return -1;
}
if (got_picture == 1)
{
printf("Succeed to encode frame: %5d\tsize:%5d\n",framecnt,pkt.size);
framecnt++;
pkt.stream_index = video_st->index;
/* 将编码后的视频码流写入文件 */
ret = av_write_frame(pFormatCtx, &pkt);
av_free_packet(&pkt);
}
j++;
}
//Flush Encoder
/* 输入的像素数据读取完成后调用此函数。用于输出编码器中剩余的AVPacket */
ret = flush_encoder(pFormatCtx, 0);
if (ret < 0)
{
printf("Flushing encoder failed\n");
return -1;
}
//Write file trailer
/* 写文件尾(对于某些没有文件头的封装格式,不需要此函数。比如说MPEG2TS) */
av_write_trailer(pFormatCtx);
//Clean
if (video_st)
{
avcodec_close(video_st->codec);
av_free(pFrame);
av_free(picture_buf);
}
avio_close(pFormatCtx->pb);
avformat_free_context(pFormatCtx);
av_free_packet(&pkt);
fclose(in_file);
return 0;
}