MATLAB: How to convert video file to bitstream in matlab

video

Hi, Do you know, how can i convert a video file with avi format to bitstream in Matab? i should convert avi file to bitstream and then send it as 2048-by-1 column vectors to a channel. it would be appreciated if you could help me.

Best Answer

You can use fopen/fread/fclose to read the file as a stream of bytes, which you can then convert to bits and send in whatever format you like.

Note that the receiving end might need to write the received data to a file in order to be able to display the AVI. This is because there is a difference between the video file (that you are asking to send) and the video content, and most commonly systems only have operations to display individual frames (decoded content) from memory, or to decode AVI files from files; in cases where they have operations to decode AVI streams, the streams are not going to be in the same format as files.

Related Solutions

MATLAB: How to convert a video to OFDM frames

No, it is not possible to convert directly.

You have two choices:

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
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.

MATLAB: How to convert bitstream to packets and bitxor function

You're storing your bitstream as a logical array. In that case, it's a logical operation that you want to perform, not a bitwise xor. Therefore use xor instead of bitxor.

Compare

n1 = 8; n2=32
n1logicalbit = dec2bin(n1, 8) - '0';  %gives [0 0 0 0 1 0 0 0]
n2logicalbit = dec2bin(n2, 8) - '0';  %gives [0 0 1 0 0 0 0 0]
logicalxor = xor(n1logicalbit, n2logicalbit); %gives [0 0 1 0 1 0 0 0]
binaryxor = bitxor(n1, n2); %gives 40
isequal(logicalxor, dec2bin(binaryxor, 8)-'0') %return true

Otherwise your code is fine. There's a few unnecessary transpositions, you could simply do:

bytelist = fread(fid, '*uint8'); %no transpose
bitexpanded = dec2bin(bytelist, 8) -'0'; %no colon which in your case just transposed

I would also move the fclose to just after you've done the fread. This way if your code stops further down because of an error or the user interrupting it, the file won't be left open.

Best Answer

Related Solutions

MATLAB: How to convert a video to OFDM frames

MATLAB: How to convert bitstream to packets and bitxor function

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