About recording audio

If you record audio, it is important that you note the following:

Your system only records incoming audio (from microphones). The system does not record outgoing audio (from speakers).
Audio recording affects video storage capacity. The system records audio to the associated camera’s database. Therefore, it is important to bear in mind that the database is likely to become full earlier if you record audio and video than if you only record video. The fact that the database becomes full is not in itself a problem since your system automatically archives data if the database becomes full. However, you may need additional archiving space if you record audio.
- Example: If you use MPEG4, each one-second video GOP (Group Of Pictures) are stored in one record in the database. Each second of audio is stored in one record in the database. This reduces the database’s video storage capacity to half its capacity, because half of the database’s records is used for storing audio. Consequently, the database runs full sooner, and automatic archiving takes place more often than if you were only recording video.
- Example: If you use MJPEG, audio is stored in one record for every JPEG for as long as the audio block size does not exceed the time between the JPEGs. In extreme cases, this reduces the database’s video storage capacity to half its capacity, because half of the database’s records is used for storing audio. If you use very high frame rates, which means less time between each JPEG, a smaller portion of the database is used for storing audio records, and consequently a larger portion is available for storing video. The result is that the database runs full sooner, and automatic archiving takes place more often than if you were only recording video.

The above examples are simplified. The exact available video storage capacity also depends on GOP/JPEG and audio kilobyte size.