Sound distribution and codecs Flashcards
What a codec is
A codec is a program or device that is used to make audio and video files smaller without losing too much of the quality. It uses different techniques to compress and decompress the data. Different codecs can make the files smaller or larger depending on the method they use
How quantization noise affects signal quality and how it relates to the number of bits used for quantization
It affects the signal quality by introducing errors in the digital signal. The number of bits used for quantization affects the amount of quantization noise, the more bits used, the less noise and better the signal quality.
What a WAVE file is
A WAVE file, also known as a WAV file, is a file format for storing digital audio. It stores audio in uncompressed form and it is widely used for storing and transmitting high-quality audio like music and speech recordings. It is compatible with most audio software and hardware.
What the clever tricks between audio codecs are (including level adaptation, predictive coding, joint stereo)
Audio codecs use various clever tricks to compress audio data while minimizing the loss of audio quality. These include
level adaptation - which adjusts the loudness of the audio to a certain level to make it more consistent
predictive coding- which uses the information from previous samples to predict the next sample
joint stereo - which uses a single stereo channel to represent common information between the left and right channels, resulting in a more efficient compression. These clever tricks allow codecs to compress audio data more effectively and efficiently, resulting in smaller file sizes and better audio quality.
How predictive coding is related to the way we produce speech
Predictive coding is related to the way we produce speech as it uses the information from previous samples to predict the next sample. This is similar to the way our speech production works, where the sounds we produce are based on the sounds that came before them. Predictive coding is a method of audio compression that takes advantage of this similarity by using the information from previous samples to predict the next sample, and then only storing the difference between the prediction and the actual sample. This results in a more efficient compression and less data to be stored.
Why the masking effect is relevant for audio coding
The masking effect makes audio coding more efficient by only coding the parts of the audio that can be heard and ignoring the parts that are covered by louder sounds. This results in smaller file sizes.
How MP3 reduces the file size compared to WAVE files
MP3 uses a compression algorithm to reduce the file size of an audio file. It does this by removing certain parts of the audio that are outside the range of human hearing, and by reducing the precision of certain parts of the audio that are inside the range of human hearing. This results in a smaller file size, but also results in some loss of audio quality. WAVE files are uncompressed and therefore have a larger file size.
What other codecs are used, and what benefits they have compared to MP3 (including AAC)
MP3 is a widely used audio codec that uses a compression algorithm to reduce file size while maintaining audio quality, while other codecs such as AAC, Ogg Vorbis, FLAC, and ALAC offer different benefits. AAC (Advanced Audio Coding) is another widely used audio codec that is similar to MP3 and offers better audio quality at lower bit rates, better handling of low-bitrate, improved error resilience and more efficient for multichannel audio compared to MP3. Other codecs also have their own benefits, such as Ogg Vorbis offering similar quality as MP3 at lower bitrates and FLAC being a lossless codec which compresses audio files without losing any information
Please name two file formats (codecs) that store audio lossless.
Lossless: ALAC Apple lossless audio codec
Wav Wave format
Flac
Lossy ones: Ogg, Mp3, M4a
