how to Implement function just like get_next_frame using ffmpeg?

Question

I'm trying to implement a function which can get the next frame, but when i call this function at the 3rd time

int ret = decoder.get_next_frame(mat);
ret = decoder.get_next_frame(mat);
ret = decoder.get_next_frame(mat); // error

ffmpeg avcodec_send_packet return err, and the msg is [h264 @ 0x8bd2780] Invalid NAL unit size (10848 > 766). [h264 @ 0x8bd2780] Error splitting the input into NAL units. the var with prefix '_' are all member var

int VideoDecoder::get_next_frame(cv::Mat& mat) {
int ret = 0;
bool got_frame = false;

while (!got_frame && av_read_frame(_p_fmt_ctx, _p_packet) >= 0) {
    if (_p_packet->stream_index == _video_stream_index) {

        ret = avcodec_send_packet(_p_dec_ctx, _p_packet);

        if (ret < 0 || ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
            break;
        }   

        while (ret >= 0) {
            ret = avcodec_receive_frame(_p_dec_ctx, _p_frame);
            if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
                break;
            }   

            sws_scale(_p_img_convert_ctx, _p_frame->data, _p_frame->linesize,
                    0, _p_dec_ctx->height, _p_frame_rgb->data, _p_frame_rgb->linesize);
            mat = cv::Mat(_p_frame->height, _p_frame->width, CV_8UC3, _p_frame_rgb->data[0]);
            got_frame = true;
        }   
    }   
    av_packet_unref(_p_packet);
}   

if (got_frame) {
    return _p_dec_ctx->frame_number;
}   

return 0;
}

so what's the problem?

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the video file is ok, because if i change the code from "while (!got_frame && av_read_frame(_p_fmt_ctx, _p_packet) >= 0)" to "while ( av_read_frame(_p_fmt_ctx, _p_packet) >= 0)" all the frame can be cv::imwrite correctly — protoss
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protoss protoss · Accepted Answer · 2019-05-06T13:21:46

I re-check the code, finally found a memory err, the video data released unexpected in other place, so the above codes seems ok

how to Implement function just like get_next_frame using ffmpeg?

1 Answers