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• How to send AVPacket through a QTcpSocket.write() with all of its data ?

  24 juin 2024, par CottonBuds

  I want to send an AVPacket though a QTcpSocket.write() I tried to cast the avpacket pointer to an char * but it only shows 8 bytes of the avpacket and without the avpacket.data.

  


  

  


  here is my code

  


  void DisplayStreamServer::sendDataToClient(AVPacket* packet) {
    if (client == nullptr) {
        return;
    }


    client->write((char*) packet);
    client->waitForBytesWritten();

    av_packet_unref(packet);
    av_packet_free(&packet);
}


  


  I can see that my packet.data has data inside it using the visual studio memory viewer. but it seems like when i convert the packet to char * the data is not included

  


  

  


• convert image stream received from ros subscribe topic straight to video with ffmpeg

  20 mai 2021, par techyidiot

  What i want to do is generate a video file(mp4 or mkv format) with ffmpeg from the receiving frames simultaneously without saving images on storage. Attached below is my python ROS subscriber code.

  


  import cv2
from cv_bridge import CvBridge
import rospy
from sensor_msgs.msg import Image
import numpy as np


def callback(data):
    # Used to convert between ROS and OpenCV images
    br = CvBridge()

    # Output debugging information to the terminal
    rospy.loginfo("receiving video frame")
    # Convert ROS Image message to OpenCV image
    current_frame = br.imgmsg_to_cv2(data)

    cv2.imshow("camera", current_frame)

    cv2.waitKey(1)


def listener():
    rospy.init_node("video_sub_py", anonymous=True)
    rospy.Subscriber("video_frames", Image, callback)

    rospy.spin()

    cv2.destroyAllWindows()


if __name__ == "__main__":
    listener()


  


• mp4 And Rotation - Remove Flags But Set Rotation

  7 avril 2024, par Bud

  I'm having a hard time with the rotation on some mp4 files I have. It may well be my poor understanding, so forgive me if I set out what I know (or think I know) and then what I want to happen.

  


  An mp4 has, obviously, a right way up - that is, the way you want it to show when you watch it. Call this the orientation. This isn't metadata - it's just the way you, as a person, want to see the image, with people's heads at the top of the screen and their feet at the bottom.

  


  As part of the metadata, mp4 files have a value/parameter (I believe called 'rotate') that tells how much the mp4 needs to be rotated (0, 90, 180, 270 degrees) so that it is correctly oriented. This value/parameter is observed by some players and not by some others. So if I play my video using this player, all is good (because it observes the value/parameter) - but if I play it with that other player, everything is sideways (because it doesn't observe the value/parameter).

  


  What I want to do is orient the mp4 correctly with the value/parameter set to 0, so that no matter what player plays it, it will always be played oriented correctly (because those players that observe the value/parameter will see it's 0 and do nothing). So I think what I need to do is somehow remove the value/parameter, then rotate the mp4 to the correct orientation without using the rotate value/parameter. I'm thinking of something like what FastStone Image Viewer can do with JPGs - rotate them losslessly without setting the rotate value.

  


  I've used ffmpeg and believe that it removed the rotate value/parameter (or set it to 0) because after I used it, suddenly my video appeared sideways in Windows Explorer, where previously it had appeared right way up. But how do I now rotate it to the correct orientation without changing the rotate value/parameter ?

  


  Sorry, this is very long winded and confused. Just like me.