[Libav-user] Codec type or id mismatches.

[ABDALLAH Moussa]

Hello,

I'm trying to write a stream video from an ip camero to a file using a source that I get on the web and I got an error on the function avcodec_open2(codec_ctx, codec, NULL).
Indeed when I compile the program and I execute it this is what I get on the console : [h264 @ 0x33670c0] Codec type or id mismatches.

FFmpeg is new for me and I don't know again how it's working exactly. My question is do you know what this error means  please ?

This is the command line to compile my program : g++ -w my_streamer.cpp -o my_streamer $(pkg-config --cflags --libs libavcodec libavformat libswscale libavutil).

This is what I get on the console after execute the program (I add the number 1,2,3,4,... to find where the error appears) :

[root at localhost Téléchargements]# ./my_streamer
1
2
3
4
5
6
7
8
[h264 @ 0x42e00c0] Codec type or id mismatches

This is the source code that I get on the web :

#include <stdio.h>
#include <stdlib.h>
#include <iostream>
#include <fstream>
#include <sstream>

extern "C" {
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libavformat/avio.h>
#include <libswscale/swscale.h>
}

int main(int argc, char** argv) {
                printf("1\n");
    // Open the initial context variables that are needed
    SwsContext *img_convert_ctx;
    AVFormatContext* format_ctx = avformat_alloc_context();
    AVCodecContext* codec_ctx = NULL;
    int video_stream_index;

    // Register everything
    av_register_all();
    avformat_network_init();
                printf("2\n");
    //open RTSP
    if (avformat_open_input(&format_ctx, "http://192.9.200.121/ipcam/mjpeg.cgi",
            NULL, NULL) != 0) {
        return EXIT_FAILURE;
    }

    if (avformat_find_stream_info(format_ctx, NULL) < 0) {
        return EXIT_FAILURE;
    }
                printf("3\n");
    //search video stream
    for (int i = 0; i < format_ctx->nb_streams; i++) {
        if (format_ctx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO)
            video_stream_index = i;
    }

    AVPacket packet;
    av_init_packet(&packet);
                printf("4\n");
    //open output file
    AVFormatContext* output_ctx = avformat_alloc_context();

    AVStream* stream = NULL;
    int cnt = 0;
                printf("5\n");
    //start reading packets from stream and write them to file
    av_read_play(format_ctx);    //play RTSP
                printf("6\n");
    // Get the codec
    AVCodec *codec = NULL;
    codec = avcodec_find_decoder(AV_CODEC_ID_H264);
    if (!codec) {
        exit(1);
    }
                printf("7\n");
    // Add this to allocate the context by codec
    codec_ctx = avcodec_alloc_context3(codec);

    avcodec_get_context_defaults3(codec_ctx, codec);
    avcodec_copy_context(codec_ctx, format_ctx->streams[video_stream_index]->codec);
    std::ofstream output_file;
                printf("8\n");
    if (avcodec_open2(codec_ctx, codec, NULL) < 0)
        exit(1);
                printf("9\n");
    img_convert_ctx = sws_getContext(codec_ctx->width, codec_ctx->height,
            codec_ctx->pix_fmt, codec_ctx->width, codec_ctx->height, AV_PIX_FMT_RGB24,
            SWS_BICUBIC, NULL, NULL, NULL);
                printf("10\n");
    int size = avpicture_get_size(AV_PIX_FMT_YUV420P, codec_ctx->width,
            codec_ctx->height);
    uint8_t* picture_buffer = (uint8_t*) (av_malloc(size));
    AVFrame* picture = av_frame_alloc();
    AVFrame* picture_rgb = av_frame_alloc();
    int size2 = avpicture_get_size(AV_PIX_FMT_RGB24, codec_ctx->width,
            codec_ctx->height);
    uint8_t* picture_buffer_2 = (uint8_t*) (av_malloc(size2));
    avpicture_fill((AVPicture *) picture, picture_buffer, AV_PIX_FMT_YUV420P,
            codec_ctx->width, codec_ctx->height);
    avpicture_fill((AVPicture *) picture_rgb, picture_buffer_2, AV_PIX_FMT_RGB24,
            codec_ctx->width, codec_ctx->height);
                printf("11\n");
    while (av_read_frame(format_ctx, &packet) >= 0 && cnt < 1000) { //read ~ 1000 frames

        std::cout << "1 Frame: " << cnt << std::endl;
        if (packet.stream_index == video_stream_index) {    //packet is video
            std::cout << "2 Is Video" << std::endl;
            if (stream == NULL) {    //create stream in file
                std::cout << "3 create stream" << std::endl;
                stream = avformat_new_stream(output_ctx,
                        format_ctx->streams[video_stream_index]->codec->codec);
                avcodec_copy_context(stream->codec,
                        format_ctx->streams[video_stream_index]->codec);
                stream->sample_aspect_ratio =
                        format_ctx->streams[video_stream_index]->codec->sample_aspect_ratio;
            }
            int check = 0;
            packet.stream_index = stream->id;
            std::cout << "4 decoding" << std::endl;
            int result = avcodec_decode_video2(codec_ctx, picture, &check, &packet);
            std::cout << "Bytes decoded " << result << " check " << check
                    << std::endl;
            if (cnt > 100)    //cnt < 0)
                    {
                sws_scale(img_convert_ctx, picture->data, picture->linesize, 0,
                        codec_ctx->height, picture_rgb->data, picture_rgb->linesize);
                std::stringstream file_name;
                file_name << "test" << cnt << ".ppm";
                output_file.open(file_name.str().c_str());
                output_file << "P3 " << codec_ctx->width << " " << codec_ctx->height
                        << " 255\n";
                for (int y = 0; y < codec_ctx->height; y++) {
                    for (int x = 0; x < codec_ctx->width * 3; x++)
                        output_file
                                << (int) (picture_rgb->data[0]
                                        + y * picture_rgb->linesize[0])[x] << " ";
                }
                output_file.close();
            }
            cnt++;
        }
        av_free_packet(&packet);
        av_init_packet(&packet);
    }
    av_free(picture);
    av_free(picture_rgb);
    av_free(picture_buffer);
    av_free(picture_buffer_2);

    av_read_pause(format_ctx);
    avio_close(output_ctx->pb);
    avformat_free_context(output_ctx);

    return (EXIT_SUCCESS);
}

Thanks you very much for your help,

Moussa.
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