如何解决为什么官方的 LibAV 12 视频示例无法正常工作?
我会说标题是不言自明的,但我几乎完全复制了 LibAV right here 给出的示例,但它产生的输出视频无法播放。为什么不能播放?我是否使用了错误的文件扩展名?我不明白我在这里可能做错了什么,而且我几乎找不到关于如何在 C++ 中编码 mp4 视频的文档。
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "libavcodec/avcodec.h"
#include "libavutil/frame.h"
#include "libavutil/imgutils.h"
static void encode(AVCodecContext *enc_ctx,AVFrame *frame,AVPacket *pkt,FILE *outfile) {
int ret;
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("encoded frame %3"PRId64" (size=%5d)\n",pkt->pts,pkt->size);
fwrite(pkt->data,1,pkt->size,outfile);
av_packet_unref(pkt);
}
}
int main() {
const char *filename = "animation.mp4";
const AVCodec *codec;
AVCodecContext *c = NULL;
int i,ret,x,y;
FILE *f;
AVFrame *picture;
AVPacket *pkt;
uint8_t endcode[] = { 0,0xb7 };
if (argc <= 1) {
fprintf(stderr,"Usage: %s <output file>\n",argv[0]);
exit(0);
}
avcodec_register_all();
codec = avcodec_find_encoder(AV_CODEC_ID_MPEG1VIDEO);
if (!codec) {
fprintf(stderr,"codec not found\n");
exit(1);
}
c = avcodec_alloc_context3(codec);
picture = av_frame_alloc();
pkt = av_packet_alloc();
if (!pkt)
exit(1);
c->bit_rate = 400000;
c->width = 352;
c->height = 288;
c->time_base = (AVRational){1,25};
c->framerate = (AVRational){25,1};
c->gop_size = 10;
c->max_b_frames=1;
c->pix_fmt = AV_PIX_FMT_YUV420P;
if (avcodec_open2(c,codec,NULL) < 0) {
fprintf(stderr,"Could not open codec\n");
exit(1);
}
f = fopen(filename,"wb");
if (!f) {
fprintf(stderr,"Could not open %s\n",filename);
exit(1);
}
picture->format = c->pix_fmt;
picture->width = c->width;
picture->height = c->height;
ret = av_frame_get_buffer(picture,32);
if (ret < 0) {
fprintf(stderr,"Could not alloc the frame data\n");
exit(1);
}
for(i=0;i<25;i++) {
fflush(stdout);
ret = av_frame_make_writable(picture);
if (ret < 0)
exit(1);
for(y=0;y<c->height;y++) {
for(x=0;x<c->width;x++) {
picture->data[0][y * picture->linesize[0] + x] = x + y + i * 3;
}
}
for(y=0;y<c->height/2;y++) {
for(x=0;x<c->width/2;x++) {
picture->data[1][y * picture->linesize[1] + x] = 128 + y + i * 2;
picture->data[2][y * picture->linesize[2] + x] = 64 + x + i * 5;
}
}
picture->pts = i;
encode(c,picture,pkt,f);
}
encode(c,NULL,f);
fwrite(endcode,sizeof(endcode),f);
fclose(f);
avcodec_free_context(&c);
av_frame_free(&picture);
av_packet_free(&pkt);
return 0;
}
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