FFmpeg———encode_video(学习)
#include <iostream>
using namespace std;
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
extern"C"
{
#include "libavcodec/avcodec.h"
#include "libavutil/opt.h"
#include "libavutil/imgutils.h"
#include "libavutil/error.h"
}
static void encode(AVCodecContext* enc_ctx, AVFrame* frame, AVPacket* pkt,
FILE* outfile)
{
int ret;
/* send the frame to the encoder */
if (frame)
printf("Send frame %lld\n", frame->pts); //修改 lld 替换 PRId64
/*avcodec_send_frame 与 avcodec_receive_packet 配合使用*/
ret = avcodec_send_frame(enc_ctx, frame);
if (ret < 0) {
fprintf(stderr, "Error sending a frame for encoding\n");
exit(1);
}
while (ret >= 0) {
ret = avcodec_receive_packet(enc_ctx, pkt);
if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
return;
else if (ret < 0) {
fprintf(stderr, "Error during encoding\n");
exit(1);
}
printf("Write packet %lld (size=%d)\n", pkt->pts, pkt->size); //修改 lld 替换 PRId64
fwrite(pkt->data, 1, pkt->size, outfile);
av_packet_unref(pkt); //清空数据压缩包
}
}
int main()
{
const char* filename;
const AVCodec* codec;
AVCodecContext* c = NULL; // 编码器上下文
int i, ret, x, y;
FILE* f;
AVFrame* frame; // 音视频数据帧结构体
AVPacket* pkt;
uint8_t endcode[] = { 0, 0, 1, 0xb7 };
filename = "text_264";
/* find the mpeg1video encoder */
codec = avcodec_find_encoder(AV_CODEC_ID_H264);
if (!codec) {
fprintf(stderr, "Codec not found\n");
exit(1);
}
// 为编码器申请空间并设置初始值
c = avcodec_alloc_context3(codec);
if (!c) {
fprintf(stderr, "Could not allocate video codec context\n");
exit(1);
}
pkt = av_packet_alloc();
if (!pkt)
exit(1);
/* put sample parameters */
c->bit_rate = 400000;
/* 分辨率 为2的倍数 */
c->width = 352;
c->height = 288;
/* frames per second */
c->time_base.num = 1;
c->time_base.den = 25;
//帧率
c->framerate.num = 25;
c->framerate.den = 1;
/* emit one intra frame every ten frames
* check frame pict_type before passing frame
* to encoder, if frame->pict_type is AV_PICTURE_TYPE_I
* then gop_size is ignored and the output of encoder
* will always be I frame irrespective to gop_size
*/
c->gop_size = 10;
c->max_b_frames = 1; //非B帧之间的最大的B帧数
c->pix_fmt = AV_PIX_FMT_YUV420P; //像素格式
if (codec->id == AV_CODEC_ID_H264)
av_opt_set(c->priv_data, "preset", "slow", 0); //设置属性
/* open it */
ret = avcodec_open2(c, codec, NULL);
if (ret < 0) {
fprintf(stderr, "Could not open codec: %s\n", av_err2str(ret));
exit(1);
}
f = fopen(filename, "wb");
if (!f) {
fprintf(stderr, "Could not open %s\n", filename);
exit(1);
}
frame = av_frame_alloc();
if (!frame) {
fprintf(stderr, "Could not allocate video frame\n");
exit(1);
}
frame->format = c->pix_fmt;
frame->width = c->width;
frame->height = c->height;
ret = av_frame_get_buffer(frame, 0); //申请数据帧缓冲区
if (ret < 0) {
fprintf(stderr, "Could not allocate the video frame data\n");
exit(1);
}
/* encode 1 second of video */
for (i = 0; i < 25; i++) {
fflush(stdout);
/* Make sure the frame data is writable.
On the first round, the frame is fresh from av_frame_get_buffer()
and therefore we know it is writable.
But on the next rounds, encode() will have called
avcodec_send_frame(), and the codec may have kept a reference to
the frame in its internal structures, that makes the frame
unwritable.
av_frame_make_writable() checks that and allocates a new buffer
for the frame only if necessary.
*/
ret = av_frame_make_writable(frame); //确保数据帧是可写
if (ret < 0)
exit(1);
/*
模拟图片数据
*/
/* Y */
for (y = 0; y < c->height; y++) {
for (x = 0; x < c->width; x++) {
frame->data[0][y * frame->linesize[0] + x] = x + y + i * 3;
}
}
/* Cb and Cr */
for (y = 0; y < c->height / 2; y++) {
for (x = 0; x < c->width / 2; x++) {
frame->data[1][y * frame->linesize[1] + x] = 128 + y + i * 2;
frame->data[2][y * frame->linesize[2] + x] = 64 + x + i * 5;
}
}
frame->pts = i;
/* encode the image */
encode(c, frame, pkt, f);
}
/* flush the encoder */
encode(c, NULL, pkt, f);
/* Add sequence end code to have a real MPEG file.
It makes only sense because this tiny examples writes packets
directly. This is called "elementary stream" and only works for some
codecs. To create a valid file, you usually need to write packets
into a proper file format or protocol; see mux.c.
*/
if (codec->id == AV_CODEC_ID_MPEG1VIDEO || codec->id == AV_CODEC_ID_MPEG2VIDEO)
fwrite(endcode, 1, sizeof(endcode), f);
fclose(f);
avcodec_free_context(&c);
av_frame_free(&frame);
av_packet_free(&pkt);
return 0;
}