MPEG 4 file compression, what technologies are used in MPEG 4 audio compression

You can go to a format like divx, or xvid, and he's also in mpeg-4 or something, but it's less than the average one. He has a lot of compression. But there is not much loss of quality to the sound and **. It should meet your requirements.

If you want to use it on PSP, then it is recommended to use MP4 RM conversion expert, you can convert almost all ** formats to PSP MP4 format, the conversion quality and speed are very good, you can convert it by default, you can also adjust the bitrate parameter a little smaller before conversion, and the file size will be smaller.

Resources.

Answer]: MPEG-4 audio compression uses the following technologies:

1) 2 4kb s (sampling frequency is 8kHz) and 4 16kb s (sampling frequency comma rate is 8kHz and 16kHz), using LPC (low delay code excitation gesture code).

2) 6 24kb s (sampling frequency of 8kHz and Shanqi 16kHz) using CERP (code excitation linear**).

3) 16 64kb s (sampling frequency greater than 8kHz) adopts AAC.

Answer]: MPEG-4 introduces the concept of Video Object Plane (VOP). In this concept, the scene in each frame of the image sequence is seen as being composed of different VOPs according to some characteristics of interest to the face, such as shape, movement, texture, etc.

A continuous VOP of the same object is called a video object (VO). MPEG-4 introduces shape information coding, and although shape coding is not new in the fields of computer graphics, computer vision, and image compression, it is the first time that it has been included in a complete coding standard. MPEG-4 uses motion** and motion compensation techniques to remove time redundancy from image information, and the encoding techniques of these motion information can be seen as an extension of existing standards to arbitrarily shaped VOPs.

There are three modes of vop encoding, namely intra-frame encoding (i-vop), inter-frame encoding (p-vop), and bidirectionaly encoding (b-vop). Texture-encoded objects can be in intra-frame encoding mode (i-vop) or in inter-frame encoding mode B-vop or P-vop motion compensated for errors. The coding method is still basically based on the 8-8 pixel block DCT method.

In applications such as remote multi-database retrieval and content replay, the introduction of hierarchical coding enables the receiver to decode and replay multi-resolution according to specific channel bandwidth, system processing capacity, display capability and user requirements. MPEG-4 implements hierarchical encoding through the data starvation structure of the Video Object Layer.