convert audio

while (av_read_frame(pInputCtx, &pktIn) >= 0) {
            do {
                len = avcodec_decode_audio4(pInputStream->codec, frame, &got_frame, &pktIn);
                DIE_IF_LESS_ZERO(len, "Error decoding frame: %s", e2s(len));
                len = FFMIN(len, pktIn.size);
                if (len < 0) break;
                if (got_frame) {
                    do {
                        av_init_packet(&pktOut);
                        pktOut.data = NULL;
                        pktOut.size = 0;
                        LOGI("encode frame");
                        DIE_IF_UNDEFINED(pOutputStream->codec, "no output codec");
                        DIE_IF_UNDEFINED(frame->nb_samples, "no nb samples");
                        DIE_IF_UNDEFINED(pOutputStream->codec->internal, "no internal");
                        LOGI("tests done");
                        len = avcodec_encode_audio2(pOutputStream->codec, &pktOut, frame, &got_packet);
                        LOGI("encode done");
                        DIE_IF_LESS_ZERO(len, "Error (re)encoding frame: %s", e2s(len));
                    } while (!got_packet);
                    // write packet;
                    LOGI("write packet");
                    av_free_packet(&pktOut);
                }
                pktIn.data += len;
                pktIn.size -= len;
            } while (pktIn.size > 0);
            av_free_packet(&pktIn);
    }

    LOGI("write trailer");
    av_write_trailer(pOutputCtx);
    LOGI("end");