HPC Multimedia

Introduction to codec

Introduction

Here is a brief introduction to the procedures of the codecs JPEG, MPEG-4, H.264, and H.265:

  • JPEG: JPEG is a lossy compression algorithm that is commonly used for images. The JPEG compression process works by dividing the image into small blocks of pixels and then using a mathematical algorithm to reduce the number of bits needed to represent each block. The more compression that is applied, the lower the quality of the image will be.
  • MPEG-4: MPEG-4 is a family of video compression standards that are commonly used for streaming and downloading video. MPEG-4 compression works by dividing the video into small frames and then using a mathematical algorithm to reduce the number of bits needed to represent each frame. The more compression that is applied, the lower the quality of the video will be.
  • H.264: H.264 is a video compression standard that is commonly used for high-definition video. H.264 compression works by dividing the video into small frames and then using a mathematical algorithm to reduce the number of bits needed to represent each frame. H.264 is more efficient than MPEG-4, so it can achieve higher quality video with the same amount of compression.
  • H.265: H.265 is a video compression standard that is even more efficient than H.264. H.265 can achieve even higher quality video with the same amount of compression.
  • YUV: YUV is a color space that is commonly used for video. YUV is a three-component color space, with the Y component representing the brightness, the U component representing the blue-luminance, and the V component representing the red-luminance.
  • Raw: Raw is a format that stores image data without any compression. Raw images are typically larger than compressed images, but they offer the best possible image quality.

JPEG:

  • The image is divided into 8x8 blocks of pixels.
  • Each block is converted to a frequency domain using a discrete cosine transform (DCT).
  • The DCT coefficients are quantized, which means that they are rounded to a certain number of bits.
  • The quantized coefficients are then encoded using a lossless compression algorithm, such as Huffman coding.
  • The encoded coefficients are stored in a file.

MPEG-4:

  • The video is divided into frames.
  • Each frame is divided into smaller blocks of pixels.
  • Each block is converted to a frequency domain using a discrete cosine transform (DCT).
  • The DCT coefficients are quantized, which means that they are rounded to a certain number of bits.
  • The quantized coefficients are then encoded using a lossy compression algorithm, such as a variable length coding (VLC) algorithm.
  • The encoded coefficients are stored in a file.

H.264:

  • The video is divided into frames.
  • Each frame is divided into smaller blocks of pixels.
  • Each block is converted to a frequency domain using a discrete cosine transform (DCT).
  • The DCT coefficients are quantized, which means that they are rounded to a certain number of bits.
  • The quantized coefficients are then encoded using a lossy compression algorithm, such as a context-adaptive variable length coding (CAVLC) algorithm.
  • The encoded coefficients are stored in a file.

H.265:

  • The video is divided into frames.
  • Each frame is divided into smaller blocks of pixels.
  • Each block is converted to a frequency domain using a discrete cosine transform (DCT).
  • The DCT coefficients are quantized, which means that they are rounded to a certain number of bits.
  • The quantized coefficients are then encoded using a lossy compression algorithm, such as a range-adaptive hybrid coding (RACH) algorithm.
  • The encoded coefficients are stored in a file.

YUV:

  • The image is divided into three channels: Y, U, and V.
  • Each channel is then converted to a range of values between 0 and 255.
  • The channels are then stored in a file.

Raw:

  • The image data is stored without any compression.
  • The image data is then stored in a file.