Audio Transcoding using FFmpeg - error

        /*
         * File:   main.cpp
         * Author: vinod
         * Compile with "g++ -std=c++11 -o audiotranscode main.cpp -lavformat -lavcodec -lavutil -lavfilter"
         *
         */


        #if !defined PRId64 || PRI_MACROS_BROKEN
        #undef PRId64
        #define PRId64 "lld"
        #endif

        #define __STDC_FORMAT_MACROS

        #ifdef   __cplusplus
        extern "C" {
        #endif

        #include <stdio.h>
        #include <stdlib.h>
        #include <sys/types.h>
        #include <stdint.h>
        #include <libavutil/imgutils.h>
        #include <libavutil/samplefmt.h>
        #include <libavutil/frame.h>
        #include <libavutil/timestamp.h>
        #include <libavformat/avformat.h>
        #include <libavfilter/avfilter.h>
        #include <libavfilter/buffersrc.h>
        #include <libavfilter/buffersink.h>
        #include <libswscale/swscale.h>
        #include <libavutil/opt.h>

        #ifdef   __cplusplus
        }
        #endif

        #include <iostream>
        using namespace std;

        int select_stream, got_frame, got_packet;

        AVFormatContext *in_fmt_ctx = NULL, *out_fmt_ctx = NULL;
        AVCodec *dec_codec = NULL, * enc_codec = NULL;
        AVStream *audio_st = NULL;
        AVCodecContext *enc_ctx = NULL, *dec_ctx = NULL;

        AVFrame *pFrame = NULL, * pFrameFiltered = NULL;

        AVFilterGraph *filter_graph = NULL;
        AVFilterContext *buffersrc_ctx = NULL;
        AVFilterContext *buffersink_ctx = NULL;

        AVPacket packet;

        string inFileName = "/home/vinod/vinod/Media/univac.webm";
        string outFileName = "audio_extracted.m4a";

        int target_bit_rate = 128000,
            sample_rate = 22050,
            channels = 1;
        AVSampleFormat sample_fmt = AV_SAMPLE_FMT_S16;
        string filter_description = "aresample=22050,aformat=sample_fmts=s16:channel_layouts=mono";

        int log_averror(int errcode)
        {
                char *errbuf = (char *) calloc(AV_ERROR_MAX_STRING_SIZE, sizeof(char));
                av_strerror(errcode, errbuf, AV_ERROR_MAX_STRING_SIZE);
                std::cout << "Error - " << errbuf << std::endl;
                delete [] errbuf;
                return -1;
        }

        /**
         * Initialize conversion filter */
        int initialize_audio_filter()
        {
                char args[512];
                int ret;
                AVFilter *buffersrc = avfilter_get_by_name("abuffer");
                AVFilter *buffersink = avfilter_get_by_name("abuffersink");
                AVFilterInOut *outputs = avfilter_inout_alloc();
                AVFilterInOut *inputs = avfilter_inout_alloc();
                filter_graph = avfilter_graph_alloc();
                const enum AVSampleFormat out_sample_fmts[] = {sample_fmt, AV_SAMPLE_FMT_NONE};
                const int64_t out_channel_layouts[] = {av_get_default_channel_layout(out_fmt_ctx -> streams[0] -> codec -> channels), -1};
                const int out_sample_rates[] = {out_fmt_ctx -> streams[0] -> codec -> sample_rate, -1};

                if (!dec_ctx->channel_layout)
                        dec_ctx->channel_layout = av_get_default_channel_layout(dec_ctx->channels);

                snprintf(args, sizeof(args), "time_base=%d/%d:sample_rate=%d:sample_fmt=%s:channel_layout=0x%" PRIx64,
                         in_fmt_ctx -> streams[select_stream] -> time_base.num, in_fmt_ctx -> streams[select_stream] -> time_base.den,
                         dec_ctx->sample_rate,
                         av_get_sample_fmt_name(dec_ctx->sample_fmt),
                         dec_ctx->channel_layout);
                ret = avfilter_graph_create_filter(&buffersrc_ctx, buffersrc, "in", args, NULL, filter_graph);

                if (ret < 0) {
                        av_log(NULL, AV_LOG_ERROR, "Cannot create buffer source\n");
                        return -1;
                }

                ret = avfilter_graph_create_filter(&buffersink_ctx, buffersink, "out", NULL, NULL, filter_graph);

                if (ret < 0) {
                        av_log(NULL, AV_LOG_ERROR, "Cannot create buffer sink\n");
                        return ret;
                }

                ret = av_opt_set_int_list(buffersink_ctx, "sample_fmts", out_sample_fmts, -1,
                                          AV_OPT_SEARCH_CHILDREN);

                if (ret < 0) {
                        av_log(NULL, AV_LOG_ERROR, "Cannot set output sample format\n");
                        return ret;
                }

                ret = av_opt_set_int_list(buffersink_ctx, "channel_layouts", out_channel_layouts, -1,
                                          AV_OPT_SEARCH_CHILDREN);

                if (ret < 0) {
                        av_log(NULL, AV_LOG_ERROR, "Cannot set output channel layout\n");
                        return ret;
                }

                ret = av_opt_set_int_list(buffersink_ctx, "sample_rates", out_sample_rates, -1,
                                          AV_OPT_SEARCH_CHILDREN);

                if (ret < 0) {
                        av_log(NULL, AV_LOG_ERROR, "Cannot set output sample rate\n");
                        return ret;
                }

                /* Endpoints for the filter graph. */
                outputs -> name = av_strdup("in");
                outputs -> filter_ctx = buffersrc_ctx;
                outputs -> pad_idx = 0;
                outputs -> next = NULL;
                /* Endpoints for the filter graph. */
                inputs -> name = av_strdup("out");
                inputs -> filter_ctx = buffersink_ctx;
                inputs -> pad_idx = 0;
                inputs -> next = NULL;
                string filter_desc = filter_description;

                if ((ret = avfilter_graph_parse_ptr(filter_graph, filter_desc.c_str(), &inputs, &outputs, NULL)) < 0) {
                        log_averror(ret);
                        exit(1);
                }

                if ((ret = avfilter_graph_config(filter_graph, NULL)) < 0) {
                        log_averror(ret);
                        exit(1);
                }

                /* Print summary of the sink buffer
                 * Note: args buffer is reused to store channel layout string */
                AVFilterLink *outlink = buffersink_ctx->inputs[0];
                av_get_channel_layout_string(args, sizeof(args), -1, outlink->channel_layout);
                av_log(NULL, AV_LOG_INFO, "Output: srate:%dHz fmt:%s chlayout:%s\n",
                       (int) outlink->sample_rate,
                       (char *) av_x_if_null(av_get_sample_fmt_name((AVSampleFormat) outlink->format), "?"),
                       args);
                return 0;
        }

        /*
         *
         */
        int main(int argc, char **argv)
        {
                int ret;
                cout << "Hello World" << endl;
                printf("abcd");
                avcodec_register_all();
                av_register_all();
                avfilter_register_all();

                /* open input file, and allocate format context */
                if (avformat_open_input(&in_fmt_ctx, inFileName.c_str(), NULL, NULL) < 0) {
                        std::cout << "error opening input file - " << inFileName << std::endl;
                        return -1;
                }

                /* retrieve stream information */
                if (avformat_find_stream_info(in_fmt_ctx, NULL) < 0) {
                        std::cerr << "Could not find stream information in the input file " << inFileName << std::endl;
                }

                /* Dump format details */
                printf("\n ---------------------------------------------------------------------- \n");
                av_dump_format(in_fmt_ctx, 0, inFileName.c_str(), 0);
                printf("\n ---------------------------------------------------------------------- \n");
                /* Choose a audio stream */
                select_stream = av_find_best_stream(in_fmt_ctx, AVMEDIA_TYPE_AUDIO, -1, -1, &dec_codec, 0);

                if (select_stream == AVERROR_STREAM_NOT_FOUND) {
                        std::cerr << "No audio stream found" << std::endl;
                        return -1;
                }

                if (select_stream == AVERROR_DECODER_NOT_FOUND) {
                        std::cerr << "No suitable decoder found" << std::endl;
                        return -1;
                }

                dec_ctx = in_fmt_ctx -> streams[ select_stream] -> codec;
                av_opt_set_int(dec_ctx, "refcounted_frames", 1, 0);

                /* init the audio decoder */
                if ((ret = avcodec_open2(dec_ctx, dec_codec, NULL)) < 0) {
                        av_log(NULL, AV_LOG_ERROR, "Cannot open audio decoder\n");
                        return ret;
                }

                /* allocate output context */
                ret = avformat_alloc_output_context2(&out_fmt_ctx, NULL, NULL,
                                                     outFileName.c_str());

                if (ret < 0) {
                        std::cerr << "Could not create output context for the file " << outFileName << std::endl;
                        return -1;
                }

                /* find the encoder */
                enum AVCodecID codec_id = out_fmt_ctx -> oformat -> audio_codec;
                enc_codec = avcodec_find_encoder(codec_id);

                if (!(enc_codec)) {
                        std::cerr << "Could not find encoder for - " << avcodec_get_name(codec_id) << std::endl;
                        return -1;
                }

                /* add a new stream */
                audio_st = avformat_new_stream(out_fmt_ctx, enc_codec);

                if (!audio_st) {
                        std::cerr << "Could not add audio stream - " << std::endl;
                }

                /* Initialise audio codec */
                audio_st -> id = out_fmt_ctx -> nb_streams - 1;
                enc_ctx = audio_st -> codec;
                enc_ctx -> codec_id = codec_id;
                enc_ctx -> codec_type = AVMEDIA_TYPE_AUDIO;
                enc_ctx -> bit_rate = target_bit_rate;
                enc_ctx -> sample_rate = sample_rate;
                enc_ctx -> sample_fmt = sample_fmt;
                enc_ctx -> channels = channels;
                enc_ctx -> channel_layout = av_get_default_channel_layout(enc_ctx -> channels);

                /* Some formats want stream headers to be separate. */
                if (out_fmt_ctx -> oformat -> flags & AVFMT_GLOBALHEADER) {
                        enc_ctx -> flags |= CODEC_FLAG_GLOBAL_HEADER;
                }

                ret = avcodec_open2(out_fmt_ctx -> streams[0] -> codec, enc_codec, NULL);

                if (ret < 0) {
                        std::cerr << "Could not create codec context for the file " << outFileName << std::endl;
                        return -1;
                }

                /* Initialize filter */
                initialize_audio_filter();

                if (!(out_fmt_ctx -> oformat -> flags & AVFMT_NOFILE)) {
                        int ret = avio_open(& out_fmt_ctx -> pb, outFileName.c_str(),
                                            AVIO_FLAG_WRITE);

                        if (ret < 0) {
                                log_averror(ret);
                                return -1;
                        }
                }

                /* Write header */
                if (avformat_write_header(out_fmt_ctx, NULL) < 0) {
                        if (ret < 0) {
                                log_averror(ret);
                                return -1;
                        }
                }

                /* Allocate frame */
                pFrame = av_frame_alloc();

                if (!pFrame) {
                        std::cerr << "Could not allocate frame\n";
                        return -1;
                }

                pFrameFiltered = av_frame_alloc();

                if (!pFrameFiltered) {
                        std::cerr << "Could not allocate frame\n";
                        return -1;
                }

                av_init_packet(&packet);
                packet.data = NULL;
                packet.size = 0;

                /* Read packet from the stream */
                while (av_read_frame(in_fmt_ctx, &packet) >= 0) {
                        if (packet.stream_index == select_stream) {
                                avcodec_get_frame_defaults(pFrame);
                                ret = avcodec_decode_audio4(dec_ctx, pFrame, &got_frame, &packet);

                                if (ret < 0) {
                                        log_averror(ret);
                                        return ret;
                                }

                                printf("Decoded packet pts : %ld ", packet.pts);
                                printf("Frame Best Effor pts : %ld \n", pFrame->best_effort_timestamp);
                                /* Set frame pts */
                                pFrame -> pts = av_frame_get_best_effort_timestamp(pFrame);

                                if (got_frame) {
                                        /* push the decoded frame into the filtergraph */
                                        ret = av_buffersrc_add_frame_flags(buffersrc_ctx, pFrame, AV_BUFFERSRC_FLAG_KEEP_REF);

                                        if (ret < 0) {
                                                log_averror(ret);
                                                return ret;
                                        }

                                        /* pull filtered frames from the filtergraph */
                                        while (1) {
                                                ret = av_buffersink_get_frame(buffersink_ctx, pFrameFiltered);

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

                                                if (ret < 0) {
                                                        printf("Error while getting filtered frames from filtergraph\n");
                                                        log_averror(ret);
                                                        return -1;
                                                }

                                                /* Initialize the packets */
                                                AVPacket encodedPacket = {0};
                                                av_init_packet(&encodedPacket);
                                                ret = avcodec_encode_audio2(out_fmt_ctx -> streams[0] -> codec, &encodedPacket, pFrameFiltered, &got_packet);

                                                if (!ret && got_packet && encodedPacket.size) {
                                                        /* Set correct pts and dts */
                                                        if (encodedPacket.pts != AV_NOPTS_VALUE) {
                                                                encodedPacket.pts = av_rescale_q(encodedPacket.pts, buffersink_ctx -> inputs[0] -> time_base,
                                                                                                 out_fmt_ctx -> streams[0] -> time_base);
                                                        }

                                                        if (encodedPacket.dts != AV_NOPTS_VALUE) {
                                                                encodedPacket.dts = av_rescale_q(encodedPacket.dts, buffersink_ctx -> inputs[0] -> time_base,
                                                                                                 out_fmt_ctx -> streams[0] -> time_base);
                                                        }

                                                        printf("Encoded packet pts %ld\n", encodedPacket.pts);
                                                        /* Write the compressed frame to the media file. */
                                                        ret = av_interleaved_write_frame(out_fmt_ctx, &encodedPacket);

                                                        if (ret < 0) {
                                                                log_averror(ret);
                                                                return -1;
                                                        }
                                                } else if (ret < 0) {
                                                        log_averror(ret);
                                                        return -1;
                                                }

                                                av_frame_unref(pFrameFiltered);
                                        }

                                        av_frame_unref(pFrame);
                                }
                        }
                }

                /* Flush delayed frames from encoder*/
                while (got_packet) {
                        AVPacket encodedPacket = {0};
                        av_init_packet(&encodedPacket);
                        ret = avcodec_encode_audio2(out_fmt_ctx -> streams[0] -> codec, &encodedPacket, NULL, &got_packet);

                        if (!ret && got_packet && encodedPacket.size) {
                                /* Set correct pts and dts */
                                if (encodedPacket.pts != AV_NOPTS_VALUE) {
                                        encodedPacket.pts = av_rescale_q(encodedPacket.pts, buffersink_ctx -> inputs[0] -> time_base,
                                                                         out_fmt_ctx -> streams[0] -> time_base);
                                }

                                if (encodedPacket.dts != AV_NOPTS_VALUE) {
                                        encodedPacket.dts = av_rescale_q(encodedPacket.dts, buffersink_ctx -> inputs[0] -> time_base,
                                                                         out_fmt_ctx -> streams[0] -> time_base);
                                }

                                printf("Encoded packet pts %ld\n", encodedPacket.pts);
                                /* Write the compressed frame to the media file. */
                                ret = av_interleaved_write_frame(out_fmt_ctx, &encodedPacket);

                                if (ret < 0) {
                                        log_averror(ret);
                                        return -1;
                                }
                        } else if (ret < 0) {
                                log_averror(ret);
                                return -1;
                        }
                }

                /* Write Trailer */
                av_write_trailer(out_fmt_ctx);
                avfilter_graph_free(&filter_graph);

                if (dec_ctx)
                        avcodec_close(dec_ctx);

                avformat_close_input(&in_fmt_ctx);
                av_frame_free(&pFrame);
                av_frame_free(&pFrameFiltered);

                if (!(out_fmt_ctx -> oformat -> flags & AVFMT_NOFILE))
                        avio_close(out_fmt_ctx -> pb);

                avformat_free_context(out_fmt_ctx);
                return 0;
        }