AAC: super low bit rate but still acceptableAAC uses a standard MPEG-2 and MPEG-4. AAC standard is already present for a long time, since 1997. However, due to various limitations, this standard does not expand as fast as its competitors relative.
AAC also expanded into three variants of the popular. Variants include AAC, AACPlus v1, v2 and AACPlus. Sometimes, there are different variants of names, such as LC AAC, eAAC, eAAC +, HE-AAC, and others. However, there are really only three main variants of the AAC format.
Parametric Stereo: Can you save the bit rate by sending an audio signal into a form monoaural.
Spectral Band Replication (SBR):
Spectral Band Replication (SBR):
duplication of the audio bandwidth Most existing audio formats tends to reduce the bandwidth if the bit rate used was too small. For example, the bit rate of 128 Kbps, MP3 format can provide bandwidth up to 20 kHz. If bit rate is halved (64 Kbps), the bandwidth that is able to produce only about 10 kHz only. Audio frequencies above 10 kHz auto-cut or in other words will not be saved. AAC with SBR mechanism enables a wider bandwidth at a small bit rate. Based on specifications, SBR was able to maintain the bandwidth to more than 15 kHz at low bit rates.
How can it be done? The truth is simple. Part Maker (encoder) will only store data required (approximately half of the bandwidth) plus any other information needed to reconstruct the data being transmitted. Additional bandwidth will be made by the receiver (decoder). Special algorithm will make a full re frequency based on analysis of existing data. This method is certainly more efficient than if the encoder had to save bandwidth in full.
How can it be done? The truth is simple. Part Maker (encoder) will only store data required (approximately half of the bandwidth) plus any other information needed to reconstruct the data being transmitted. Additional bandwidth will be made by the receiver (decoder). Special algorithm will make a full re frequency based on analysis of existing data. This method is certainly more efficient than if the encoder had to save bandwidth in full.
Three variants: Addition of Spectral Band Replication algorithm (SBR) and parametric stereo (PS) determines the type of AAC format that will be generated.
SBR will be very effective for low to medium bit rate. In addition to AAC (AACPlus v1), SBR technique is also used in MP3 format, known as MP3PRO.
Parametric stereo: more frugal with the signal monoauralParametric stereo (PS) is a standard for AACPlus v2. PS is optimized for very low bit rate (16-40 kbps only). According to specifications, using this PS, it is a good audio quality can be enjoyed only by a bit rate of 24 Kbps.
SBR will be very effective for low to medium bit rate. In addition to AAC (AACPlus v1), SBR technique is also used in MP3 format, known as MP3PRO.
Parametric stereo: more frugal with the signal monoauralParametric stereo (PS) is a standard for AACPlus v2. PS is optimized for very low bit rate (16-40 kbps only). According to specifications, using this PS, it is a good audio quality can be enjoyed only by a bit rate of 24 Kbps.
