HOW TO COMPRESS SOUND FILE THEORY MOVIE
Lets imagine we record a 5 minute movie of a cat playing, uncompressed and recorded at 1080p(1920×1080) Without video compression, video files would be HUGE!!!! This is where each section of audio is recorded using a different bit rate, depending on the nature and complexity of the audio wave at that point, higher bit rates for detailed and human ear sensitive parts, lower bit rates for other parts, however that average bit rate for the file still stays at the overall bit rate. One major compression technique used is Variable Bit Rate. Audio masking means that some sounds can’t be perceived when in the presence of another sound and therefore can be discarded.Ĭonstant Bit Rate (CBR) vs Variable Bit Rate(VBR).Humans can only detect pitch changes great than a certain amount and therefore smaller changes can be discarded or describe in less detail.Humans can only hear sounds between certain frequencies, so extremely high or low frequencies can be discarded, or reduced in the number of bits used to describe them.
Lossy Audio compression uses learning from Psychoacoustics(the study of the psychology of sound) to apply compression of audio files. Most high quality lossy compression algorithms allow you to reduce the file size to 128 Kb per seconds, a massive 97% reduction from the 5.6 Megabits per second above! You would use up your entire month’s data allowance in less than 4 hours of listening to Spotify! While modern 4G/5G data streams can cope with this draw, if your mobile data allowance was 10GB per month then:ġ0,000,000,000 / 700,000 = 14285 seconds = 238 minutes = 3.96 Hours Raw audio size = 0.7 Megabytes (5.6 Megabits per second). Raw audio size = 44,100Hz x 2 (16 bits = 2 bytes) Most CD quality audio data is recorded at a sampling rate of 44,100Hz (samples per second) and a sampling resolution of 16 Bits per sample.
0 kommentar(er)
