android-Mobile Multimedia Programming

1. multimedia file format

The file format defines how the physical files are organized and stored on the file system. An ordinary audio file, it has two main

Components: Metadata (title, lyrics) and audio data. Audio data may be stored in a frame order or as a whole block.

The task of the file format is to define where the metadata is stored in the file and where the audio data is stored.

In the same vein, knowing the file format allows you to read any desired data from the file.

The structure for the MP3 file format.

2. Encode/decode

encoding/decoding is actually the process of compressing and decompressing data. Generally can compress the original file to about 87%, specialized

The compression algorithm can be compressed to around 5%~60.

By encoding, multimedia files can be divided into uncompressed, lossless compression and lossy compression Class 3.

2.1 Uncompressed (WAV)

That is, the audio or video data does not do any processing to maintain the original file size. The WAV format is an uncompressed audio

A file format that encodes any sound, either audio or mute . audio files of equal length and mute

The size of the file is the same

2.2 Lossless compression (Ape,la,flac,apple lossless,wma Lossless)

Reduce file size without loss of quality. As far as audio files are concerned, they can be pressed to the 50%~60% of the original file.

2.3 lossy compression (MPEG audio, Vorbis, WMA,ADX)

The quality is lost to a certain extent, but the size of the file is greatly reduced. As far as audio is concerned, it can be pressed to 5%~20%.

MIDI Audio Format: is a protocol that does not contain any audio data and contains only instructions for producing a particular sound, instructions

Includes the sound of what MIDI device is called, the strength and duration of the sound. The computer gave these instructions to

Sound card to synthesize the corresponding sound. So the file is very small, a few minutes of MIDI only a few kilobytes.

Common formats:. OTA/.IMY/.MID/.XMF/.RTX/.RTTTL/.MXMF

android-Mobile Multimedia Programming