[Libav-user] Encoding flv video by libavcodec not working

[Mark Ma]

On 2013/11/25 21:45, Mark Ma wrote:
> Hi, everyone.
> I'm trying to use libavcodec to encode a flv video. Following code is 
> a sample code to generate a mpeg video, it works well. But after 
> replacing the codec ID with AV_CODEC_ID_FLV1, the generated video file 
> cannot be played.
>
> I opened the generated file and checked the first 4 bytes (previous 
> tag size), but it's not 0. I'm curious whether converted packet is 
> valid flv packet?
> Any suggestion is appreciated.
>
> (Code)
> |void simpleEncode(){
>      AVCodec *codec = avcodec_find_encoder(AV_CODEC_ID_MPEG1VIDEO);
>      AVCodecContext *ctx = avcodec_alloc_context3(codec);
>      ctx->bit_rate = 400000;
>      ctx->width = 352;
>      ctx->height = 288;
>      AVRational time_base = {1,25};
>      ctx->time_base = time_base;
>      ctx->gop_size = 10;
>      ctx->pix_fmt = AV_PIX_FMT_YUV420P;
>
>      avcodec_open2(ctx, codec, NULL);
>
>      AVFrame *frame = av_frame_alloc();
>      av_image_alloc(frame->data, frame->linesize, ctx->width, ctx->height, ctx->pix_fmt, 32);
>      frame->format = ctx->pix_fmt;
>      frame->height = ctx->height;
>      frame->width = ctx->width;
>
>      AVPacket pkt;
>      int got_output;
>      FILE *f = fopen("test.mpg", "wb");
>      for(int i=0; i<25; i++){
>          av_init_packet(&pkt);
>          pkt.data = NULL;
>          pkt.size = 0;
>
>          for(int w=0; w<ctx->width; w++){
>              for(int h=0; h<ctx->height; h++){
>                  frame->data[0][h*frame->linesize[0]+w]=i*10;
>              }
>          }
>          for(int w=0; w<ctx->width/2; w++){
>              for(int h=0; h<ctx->height/2; h++){
>                  frame->data[1][h*frame->linesize[1]+w]=i*10;
>                  frame->data[2][h*frame->linesize[2]+w]=i*10;
>              }
>          }
>
>          frame->pts=i;
>          avcodec_encode_video2(ctx, &pkt, frame, &got_output);
>
>          fwrite(pkt.data, 1, pkt.size, f);
>      }
> }|

Now it's solved by adding flv file header and tag header manually in the 
code.
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