最新ffmpeg，提取音频，pts设置问题，求救啊！！！！

[haitao111313]

while (av_read_frame(ic, &packet) >= 0) {
                if (packet.stream_index == videoindex + 111) {
                } else if (packet.stream_index == audioindex) {
                        int ret = 0;
                        while (packet.size > 0) {
                                out_buf = NULL;
                                if (packet.size > 0)
                                        samples = (short *) av_fast_realloc(samples, &samples_size,
                                                        FFMAX(packet.size*sizeof
                                                                        (*samples),2000)); 
                                LOGI("LOGI----------------19 ");

                                ret = avcodec_decode_audio4(aCodecCtx, oAFrame, &frameFinished2,
                                                &packet);
//                   ret = avcodec_decode_audio3(aCodecCtx,samples,&out_size,&packet);//若为音频包，解码该音频包
                                LOGI("retretret:%d", ret);
                                if (ret < 0) {
                                        LOGI("while decode audio failure\n");
                                        exit(0);
                                }
                                packet.data += ret;
                                packet.size -= ret;
                                av_fifo_generic_write(fifo,oAFrame->data[0],oAFrame->linesize[0],NULL);
                                if (frameFinished2) {
                                        out_buf = (uint8_t *) samples;
                                        AVPacket pkt;
                                        av_init_packet(&pkt);
                                        pkt.data = NULL;
                                        pkt.size = 0;
                                        ret1 = avcodec_encode_audio2(oAcc, &pkt, oAFrame,
                                                        &got_output);
                                        if (ret1 < 0) {
                                                fprintf(stderr, "Error encoding audio frame\n");
                                                exit(1);
                                        }
                                        if (got_output) {

                                                if (oAcc->coded_frame&& oAcc->coded_frame->pts != AV_NOPTS_VALUE) {
                                pkt.pts= av_rescale_q(oAcc->coded_frame->pts, oAcc->time_base, audio_st->time_base);
                                                }
                                                pkt.flags |= AV_PKT_FLAG_KEY;
                                                pkt.stream_index = audioindex;
                                                av_write_frame(oc, &pkt);
                                                av_free_packet(&pkt);
                                                m_nAudioTimeStamp++;
                                        }
                                }
                        

                        }
                }
                
                av_free_packet(&packet);
        }

上面是从mp4文件提取音频生成mp4文件的主要代码，报错：Encoder did not produce proper pts, making some up.
但是如果从mp3文件提取音频生成mp4，就不会报错，这个pkt的pts到底该怎么设置？ 我的编码器的属性设置完全是按照解码器来设置的！！！！！！
如果直接用fwrite写成aac文件也是没有问题的，但是我现在的需求就是要从mp4文件提取音频，怎么办？？？？