[Libav-user] Is the max fps of gdigrab to grab desktop only 15 frame/s??

[Maminxuan]

Hi,
         I used gdigrab to grab desktop. I set the framerate to 30, but, actually, the framerate was only 15 in my test. Why?
         Here is the options of my desktop:
         [cid:image001.png at 01D24692.EAF99380]

         Here is my code:
         ……
         av_dict_set(&options,"framerate","30",0);
    AVInputFormat *ifmt = av_find_input_format("gdigrab");
    if (avformat_open_input(&fct, "desktop", ifmt, &options) != 0){
        printf("Couldn't open input stream\n");
        return -1;
    }
    ……
    while(av_read_frame(vs->in_fct, packet)>=0)
    {
        icount++;
        finish = clock();
        duration = (double)(finish - start) / CLOCKS_PER_SEC;
        printf("%f seconds, count: %d\n", duration, icount);
        start = clock();
        av_free_packet(packet);
    }

    Here is the result:
[cid:image002.png at 01D24692.EAF99380]
         From the result, we can see, the average time was 60ms to get one picture. Why was it so slow? Were there any options about it to increase the fps?
         Thank you and look forward for your mail.


Best wish
Jack

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