how to convert a video to OFDM frames ?

Is it possible to convert directly a short video to OFDM frames ?

Answer 1

[Walter Roberson]

No, it is not possible to convert directly.

You have two choices:

1. You can read a frame of the video at a time, and convert the digital array representing each video frame to a series of OFDM frames; or
2. You can read a video file as a plain array of binary data (such as uint8) and convert the stream to a series of OFDM frames. This would not need to have any knowledge of what was in the file -- you would do exactly the same thing for video files or audio files or spreadsheets or seismometer readings. Any file can be read as a stream of bytes.

The approach you would take would depend on what you intend to do with the OFDM frames. If the point is to transmit a video stream over OFDM, for viewing purposes (such as Video On Demand) then you would want to convert frame by frame. If, though, the purpose is to copy data from one place to another, then treat it as a plain stream of bytes.

Either way, once the video (or file) is read into the computer, the process of forming OFDM packets does not care where the data came from -- though if you are doing video streaming you would want to add in some kind of protocol announcing start of frame, frame size, timestamp, and so on.

[Baghdadi Aya]

thanks a lot for your explictaion, which can guarantee the quality of video reception .?

and can you help me and give me an exemple of code that can read a frame of the video at a time and convert thr digital array to series of OFDM frames

[Walter Roberson]

OFDM cannot guarantee the quality of received data.

OFDM is a way to encode data in parallel streams for faster transmission in an environment that might have some noise in it. It has features that reduce the effect of noise. However any error detection and error correction is the responsibility of lower-level streams. The lower-level streams might or might not be encoding a protocol that offers some kind of "reliable" data transmission.

If someone puts an EMF shield over the transmitter, then it does not matter how good the signal encoding is: the signal is not going to reach the other side. And the other side might not even notice the missing data.

You should be using a protocol such as RTSP, with the bits encoded as something like QAM, and the QAM layered into OFDM.

Reading video:

https://www.mathworks.com/help/matlab/ref/videoreader.html#busqe2j-2

[Baghdadi Aya]

I decompose the video under images then I want to convert them into a binary sequence .

have you any idea how can i solve it? by the way i want the output sequence will saved in a text file ?

[Walter Roberson]

Assuming ImageArray is uint8:

bitstream = reshape((dec2bin(ImageArray, 8)-'0').', 1, []);

If you want to save that in a text file of '1' and '0' then

bit_text = reshape((dec2bin(ImageArray, 8)).', 1, []);