MJPEG vs. MPEG
In MJPEG each video frame of the digital video sequence which includes video plus closed captioning and subtitles (metadata) are separately compressed as JPEG image. It is a video compression format. It is an application of multimedia PC and is now used in digital camera, webcams, and IP cameras and also in video editing system (nonlinear).
There are many flavors of MPEG (1 2, 1 Part2, 4, etc.). In MJPEG each frame is compressed separately giving distinct frames like 24, 25, 30 per second whereas in MPEG groups of frames together are considered and then MPEG compresses together these groups of frames and interconnect them. Editing is difficult in MPEG as compared to MJPEG.
MJPEG is a lossless compression technique in which the lost data is very little so it is a better compression technique as compare to MPEG which is lossy compression technique because if the compression is less, then the recorded images and playback will be better. So in this sense, MJPEG (lossless) is better than the MPEG (lossy).
If MPEG is used in place of MJPEG than the variable F (the video frame rate in frames per second) is affected because in case of MPEG-1 the video output is 15 frames per second and in MPEG-2 the video output is 30 frames per second. Also the MJPEG is based on still images and MPEG is based on a group of images so the variable F (frame rate in frames/s) will be changed.
The literal meaning of steganography is covered writing. The history of steganography goes back to ancient Greece when the common practices of steganography was to etch messages written in wooden tablets and hide them using wax or shave the head of the messenger and tattooed it and then let the hair grow back on his head, and when the messenger reaches the contact point, his head is shaved again.
Steganography is an art and science of keeping information hide and this is done by embed the message within the other message. It works when the bits of unused or useless data in computer files like sound, HTML, graphics, text or floppy disks are replaced by the bits invisible information. The information which is hidden can be ciphertext, plain text or images. It is used sometimes when the encryption is not allowed or commonly used for supplement encryption. Using the steganography the encrypted file hides the information. So the hidden message is still invisible even if the file is deciphered. For steganography special software are also used.
Steganography can be used in different ways one of them is statistics-aware embedding. In some other algorithms, embedding causes distortion because of overwriting the image data. In this technique, the global images are used.
The value of the coefficient in Discreet Cosine Transform (DCT) is either decremented or incremented when a single bit is embedded. By this, the least significant bit of DCT coefficient can be changed in two different ways. Moreover, DCT coefficients groups are created and the parity of the bit which is least significant is used as a message bit to increase more ways of embedding a single bit. Spaces for all possible changes are figured out for all DCT blocks to search a configuration which has the minimum chances of changing image statistics. Currently, the solutions are searched which maintains the block variance, blockiness and coefficient histogram. The effectiveness of this approach is still in progress.
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