Correct EOS when saving stream from USB camera
kochmmi1
kochmmi1 at fel.cvut.cz
Fri Mar 12 15:09:10 UTC 2021
I have USB camera, embedded device. I want to have the possibility to firstly
save the video from the camera to a file, later probably to display the
video and/or stream it via RTSP by means of C/c++ wrtitten app.
Now I have a working terminal command to save the given number of frames:
''' gst-launch-1.0 v4l2src device=/dev/video1 num-buffers=900 ! image/jpeg,
width=1920, height=1080, io-mode=4 ! imxvpudec ! imxvpuenc_mjpeg ! avimux !
filesink location=/some/path.avi'''. I would like to be able to save
not-defined lenght of the video (until some user input to stop it).
I have tried several approaches. Of course I can simply use some syscall,
but the problems with that are probably not necesary to list, I will not be
taking that route.
Now the next simplest (yet probably problematic if I would want to do
something else with the stream it the future) is:
``` void pipelineVideoStart(){
if (!gst_is_initialized()) {
qWarning()<<"initializing GST";
setenv("GST_DEBUG", ("*:" + std::to_string(3)).c_str(), 1);
gst_init(nullptr, nullptr);
}
GstElement *pipeline;
GstBus *bus;
GstMessage *msg;
std::string command = "v4l2src device=/dev/video1 ! image/jpeg,
width=1920, height=1080, io-mode=4 ! imxvpudec ! imxvpuenc_mjpeg ! avimux !
filesink location = /some/file.avi";
pipeline =
gst_parse_launch
(command.c_str(),
NULL);
/* Start playing */
gst_element_set_state (pipeline, GST_STATE_PLAYING);
/* Wait until error or EOS */
bus = gst_element_get_bus (pipeline);
msg =
gst_bus_timed_pop_filtered (bus, GST_CLOCK_TIME_NONE,
GstMessageType(
GST_MESSAGE_ERROR | GST_MESSAGE_EOS));
/* Free resources */
if (msg != NULL)
gst_message_unref (msg);
gst_object_unref (bus);
gst_element_set_state (pipeline, GST_STATE_NULL);
gst_object_unref (pipeline);
return;
} '''
```
Problems I find with this approach
1) Video is created, however with wrong metadata (0 seconds lenght, even
though it is playable). Because... it's never succesfully finished, is it?
How do I stop the recording?
1) zero control. I expect problems with any additional sink (appsink, rtsp
streaming)
In second approach I was trying to build the pipeline myself:
```
static GstElement *pipeline;
void gstreamerUsbCamera::selfPipelineVideo(){
if (!gst_is_initialized()) {
setenv("GST_DEBUG", ("*:" + std::to_string(3)).c_str(), 1);
gst_init(nullptr, nullptr);
}
GstCaps *caps;
GstStateChangeReturn ret;
GstElement *source, *muxer, *sink;
source = gst_element_factory_make ("v4l2src", "source");
g_object_set (source, "device", "/dev/video1", NULL);
muxer = gst_element_factory_make ("avimux", "avimux");
sink = gst_element_factory_make ("filesink", "sink");
g_object_set (sink, "location", "/mnt/ssd/someTest.avi", NULL);
pipeline = gst_pipeline_new ("pipeline_src");
if (!pipeline || !source || !muxer || !sink) {
g_printerr ("Not all elements could be created.\n");
return;
}
caps = gst_caps_new_simple ("image/jpeg",
"width", G_TYPE_INT, 1920,
"height", G_TYPE_INT, 1080,
"io-mode", G_TYPE_INT, 4,
"framerate", GST_TYPE_FRACTION, 30, 1,
"pixel-aspect-ratio", GST_TYPE_FRACTION, 1,1,
"interlace-mode", G_TYPE_STRING, "progresive",
NULL);
GstPadTemplate *template1 =
gst_element_class_get_pad_template(GST_ELEMENT_GET_CLASS(source), "src_%u");
GstPad *pad = gst_element_request_pad(src, template1, "pad",
caps);//");// gst_pad_new("source", GST_PAD_SRC);
gst_caps_unref (caps);
gst_bin_add_many (GST_BIN (pipeline), source, muxer, sink, NULL);
if (gst_element_link_many(source, muxer,sink, NULL) != TRUE) {
g_printerr ("Elements could not be linked.\n");
gst_object_unref (pipeline);
return;
}
ret = gst_element_set_state (pipeline, GST_STATE_PLAYING);
if (ret == GST_STATE_CHANGE_FAILURE) {
g_printerr ("Unable to set the pipeline to the playing state.\n");
gst_object_unref (pipeline);
return;
}
// Start playing
recording = true;
return;
}
int endVideoPipeline(void)
{
GstMessage *message = gst_message_new_eos(nullptr);
gst_bus_post(pipeline->bus, message);
/* Free resources */
if (message != NULL)
gst_message_unref (message);
gst_element_set_state (pipeline, GST_STATE_PAUSED);
gst_element_set_state (pipeline, GST_STATE_NULL);
gst_object_unref (pipeline);
return 1;
gst_app_src_end_of_stream(GST_APP_SRC(mGstData.appsrc));
usleep(500000); // Important
gst_element_set_state (mGstData.pipeline_src, GST_STATE_NULL);
gst_object_unref (mGstData.pipeline_src);
recording = false;
return 0;
}
```
Problems with this: 1) wrong metadata (wrong lenght in VLC) and wrong format
(the caps negotiating fails, I get 3000x4000&10fps instead of HD at 30fps). I
also tried (at some point) to use the code from
https://gist.github.com/crearo/1dc01b93b2b513e0000f183144c61b20 with some
tweaks (commented-out the displaying, since that is not what I want now, and
changed startRecording function to
```void gstreamerUsbCamera::startRecordingS() {
g_print("startRecording\n");
GstPad *sinkpad;
GstPadTemplate *templ, *temp2;
GstCaps *caps;
templ = gst_element_class_get_pad_template(GST_ELEMENT_GET_CLASS(tee),
"src_%u");
teepad = gst_element_request_pad(tee, templ, NULL, NULL);
queue_record = gst_element_factory_make("queue", "queue_record");
encoder = gst_element_factory_make("imxvpuenc", NULL);
muxer = gst_element_factory_make("avimux", NULL);
filesink = gst_element_factory_make("filesink", NULL);
g_object_set(filesink, "location", "output.avi", NULL);
caps = gst_caps_new_simple ("image/jpeg",
"width", G_TYPE_INT, 1920,
"height", G_TYPE_INT, 1080,
"io-mode", G_TYPE_INT, 4,
NULL);
temp2 = gst_element_class_get_pad_template(GST_ELEMENT_GET_CLASS(src),
"src_%u");
GstPad *pad = gst_element_request_pad(src, templ, NULL, caps);
gst_bin_add_many(GST_BIN(pipeline), queue_record, encoder, muxer,
filesink, NULL);
gst_element_link_many(queue_record, encoder, muxer, filesink, NULL);
gst_element_sync_state_with_parent(queue_record);
gst_element_sync_state_with_parent(encoder);
gst_element_sync_state_with_parent(muxer);
gst_element_sync_state_with_parent(filesink);
sinkpad = gst_element_get_static_pad(queue_record, "sink");
gst_pad_link(teepad, sinkpad);
gst_object_unref(sinkpad);
isRecording = true;
}
```
Here I get empty (0B) file at output.
Now I do think that I am aiming to some tweak of the last two mentioned
approaches. Can anyone point me in the direction of my mystakes and how to
fix them? Thank you.
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