video - ffmpeg avcodec_receive_packet 返回 -11

Question

我尝试使用 ffmpeg API 从一系列输入图像创建视频。

首先我从输入文件中读取 AVFrame 然后传递给 avcodec_send_frame() , 但是当我调用 avcodec_get_packet()要获取编码数据包，它会返回 -11(在当前状态下输出不可用)。

我只是一个初学者，所以我不知道我的代码是否有问题。

这是我的源代码:

for (unsigned int i = 0; i < nb_input; ++i) {
        const char *item = input[i];
        ret = open_input_file(item);
        if(ret < 0) {
            goto end;
        }
        packet = av_packet_alloc();
        if(packet == NULL) {
            _log_e("Cannot allocate packet");
            goto end;
        }
        ret = av_read_frame(_ifmt_ctx, packet);
        if(ret < 0) {
            goto end;
        }
        av_packet_rescale_ts(packet,
                             _ifmt_ctx->streams[0]->time_base,
                             _decode_ctx->time_base);

        ret = avcodec_send_packet(_decode_ctx, packet);
        if (ret < 0) {           
            goto end;
        }

        frame = av_frame_alloc();
        if(frame == NULL) {
            ret = AVERROR(ENOMEM);
            _log_e_2("Failed to allocate frame variable for this file : %s ", item);
            goto end;
        }
        ret = avcodec_receive_frame(_decode_ctx, frame);
        if (ret == 0) {
            /*
             * DO FILTER PROCESSING HERE
             */
        } 

        for (int j = 0; j < 25; ++j) {
            ret = avcodec_send_frame(_encode_ctx, frame);
            if (ret < 0) {
                _log_e_2("Failed to send frame at pts = %d", pts);
                goto end;
            }
            AVPacket *out_packet;
            out_packet = av_packet_alloc();
            if(out_packet == NULL) {
                _log_e_2("Failed to allocate output packet at pts = %d" , pts);
                goto end;
            }
            ret = avcodec_receive_packet(_encode_ctx, out_packet);
            if(ret < 0) {
                _log_e_2("Failed to receive encoded packet at pts = %d" , pts);
                if (ret == AVERROR(EAGAIN)) {
                    _log_e(" output is not available in the current state - user must try to send input");
                }
                else if (ret == AVERROR_EOF) {
                    _log_e(" the encoder has been fully flushed, and there will be no more output packets");
                }
                else if (ret == AVERROR(EINVAL)) {
                    _log_e(" codec is not opened");
                }
                av_packet_unref(out_packet);
                goto end;
            }
            _log_v_2("Write encoded packet at pts = %d to output file", pts);
            ret = av_interleaved_write_frame(_ofmt_ctx, out_packet);
            if (ret < 0) {
                _log_e_2("Failed to write encoded packet at pts = %d to output file", pts);
                goto end;
            }
            av_packet_unref(out_packet);
            pts++;
        }

Answer 1

编码器在输出第一个编码帧之前需要几帧输入。您必须忽略 EAGAIN 并只提供下一个输入帧。