Playback Start Time and Total Duration Issue in H264 to MP4 Conversion

Hi Team,

I encountered an issue while converting H264 encoded buffers to an mp4 file. Initially, I aimed to skip the first 20 seconds of buffers and store the ones from 21 seconds to 2 minutes. Then, I began converting these buffers to an mp4 file using appsrc elements. However, I faced a problem with the resulting video file. During playback, the video starts from the 21-second mark, whereas I expected it to start from 0 seconds. Additionally, the total duration is not displayed correctly.

Here’s the pipeline of v4l2src:

gst-launch-1.0 v4l2src device=/dev/video0 ! videoconvert ! queue ! x264enc tune=zerolatency ! identity ! fakesink

We are using the identity callback to capture the frames.

Callback Code:

// Get the source pad of the identity element
identity_src_pad = gst_element_get_static_pad(identity, "src");

// Add probe to the identity source pad
gst_pad_add_probe(identity_src_pad, GST_PAD_PROBE_TYPE_BUFFER, pad_probe_cb, pipeline, NULL);

static GstPadProbeReturn pad_probe_cb(GstPad* pad, GstPadProbeInfo* info, gpointer user_data) 
    static GstClockTime timestamp = 0;
    GstMapInfo map;
    GstBuffer* buff;
    GstBuffer* new_buffer;
    buff = gst_pad_probe_info_get_buffer(info);

    gsize buffer_size = gst_buffer_get_size(buff);
    double bufferSizeMB = static_cast<double>(buffer_size) / (1024*1024);
    guint buflen = gst_buffer_list_length(buflist);
    new_buffer = gst_buffer_copy_deep(buff);
    g_print(" timestamp : %ld\n", GST_BUFFER_PTS(new_buffer) );

    // Store the buffer in here:
    gst_buffer_list_add(buflist, new_buffer);

    return GST_PAD_PROBE_OK;

File Conversion Code (H264 encoded frames to mp4 file):

(Note: 20 seconds of buffers, equivalent to 10 FPS, have been removed)

void fileconversion()
gst_buffer_list_remove(buflist, 0, 200);  // Remove the oldest buffer from index 0 with a length of 200
void convertToMP4(GstBufferList *buflist){
    // Create pipeline for MP4 conversion.
    GstElement *pipeline, *appsrc, *videoconvert, *videoencode, *parse, *muxer, *file_sink;
    pipeline = gst_pipeline_new("MP4-pipeline");
    appsrc = gst_element_factory_make("appsrc", "source");
    parse = gst_element_factory_make("h264parse", "source-h264parse");
    muxer = gst_element_factory_make("mp4mux", "mp4-muxer");
    file_sink = gst_element_factory_make("filesink", "filesink");
                 "stream-type", 0,
                 "format", GST_FORMAT_TIME, NULL);

    // Set the resolution and framerate caps
    GstCaps *caps = gst_caps_new_simple("video/x-h264",
    "width", G_TYPE_INT, 1280,
    "height", G_TYPE_INT, 720, 
    "framerate", GST_TYPE_FRACTION, 10, 1,
    "stream-format", G_TYPE_STRING, byte-stream,
    gst_app_src_set_caps (GST_APP_SRC(appsrc),caps);


    g_object_set(G_OBJECT(muxer), "fragment-duration", 2000, NULL);

    g_object_set(file_sink, "location", camera.mp4, NULL);

    printf("Cam name is %s", prefixedFilename);

    gst_bin_add_many(GST_BIN(pipeline), appsrc,parse,muxer, file_sink, NULL);
    if (gst_element_link_many(appsrc,parse,muxer, file_sink, NULL) != TRUE)
        g_printerr("Elements could not be linked in the pipeline.\n");

    copy_buflist = gst_buffer_list_copy_deep(buflist);
    g_print("isbuffered is filled and Buffer size is %d\n", gst_buffer_list_length(copy_buflist));
    gst_element_set_state(pipeline, GST_STATE_PLAYING);

    retval = gst_app_src_push_buffer_list(GST_APP_SRC(appsrc), copy_buflist);
    g_print("RETVAL %d\n", retval);
    g_print("Sending EOS!!!!!!!");
    g_signal_emit_by_name(appsrc, "end-of-stream", &retval);

I kindly request your assistance in providing a solution to this issue as soon as possible.

Best Regards,

Any suggestions regarding my query?

Hello, did I find a solution to the problem

Hi @rtzhang ,

Can you find the solution for the above problem?

No, I have not encountered the problem you mentioned. I have encountered the following problems recently. I wonder if I can help you.