Audio data in multimedia files and streams can be transmitted in different ways. Audio can be encoded using different algorithms, including AAC, AC3/EAC3, MPEG-Audio, FLAC, OPUS, etc. However, audio streams do not have as significant a difference in bitrate between compressed and uncompressed audio as video does. Uncompressed audio is also known as PCM, which stands for Pulse Code Modulation. It refers to a method used to digitally represent analog audio signals. PCM is a standard method for converting analog audio signals into a digital format that can be stored, transmitted, and processed by various devices and systems.
Uncompressed audio has several advantages over compressed audio. First of all, PCM audio provides the best level of fidelity and accuracy in representing the original signal compared to lossy audio compression algorithms, which can reduce the quality of the audio stream. Second, due to the lack of encoding, PCM audio has better compatibility compared to compressed algorithms. PCM audio is widely supported by audio devices, software, and platforms. Almost all audio playback devices, including smartphones, computers, and audio players, can decode and play PCM audio without requiring additional conversion.
In PCM audio, the analog audio signal is sampled at regular intervals, and each sample is quantized and stored as binary value. The resulting binary data represents the amplitude of the audio signal at each sampling point. The samples are taken at a specific sampling rate, measured in samples per second (Hz), such as 44.1 kHz (44,100 samples per second) and others. The following picture shows these samples of PCM audio data in file which is opened in Virinext Bitstream Analyzer.
When transmitting PCM audio data, it is necessary to include additional metadata to provide information about the audio. The specific metadata that should be transmitted can vary depending on the application or specific requirements, but here are some commonly transmitted metadata: sample rate, bit depth (represents the number of bits used in each sample of PCM audio data), number of channels, channel configuration (describes channel mapping for multi-channel audio), full duration of the audio file, and encoding information (describes the used encoding scheme). Following image is the example of PCM audio metadata extracted from file by Virinext Bitstream Analyzer.
To analyze the details of PCM audio, you can use the Virinext Bitstream Analyzer. You can download the evaluation version on the Download page. For license acquiring please check the Buy license page. The Virinext Bitstream Analyzer is a GUI tool for both in-depth and high-level analysis of many encoding standards, including uncompressed PCM audio.