![]() There is often an impression that MPEG-4 and H.264 are therefore “lower quality” formats compared to JPEG, due to this extra temporal compression, however this is not the case: SecuritySpy provides an adjustable quality setting for each format, at the lower end of which the image will look quite degraded, but at the higher end of which the image will be indistinguishable from the original uncompressed image. The more P-frames that exist between the I-frames (known as the I-frame rate, key frame rate, or GOV length), the lower the data rate will be. This strategy results in a much lower data rate compared with JPEG, especially for video surveillance footage where the majority of the image often remains the same. MPEG-4 and H.264 differ significantly from JPEG in that they are both temporally compressed formats that is the video sequence comprises one I-frame (key frame), which encodes one entire image, followed by multiple P-frames (delta frames), which encode only changes in the image since the previous frame. H.264), it is important to bear in mind that one is not necessarily “better” than the others they all have their advantages and disadvantages. When making decisions about which video compression format to use (JPEG vs. This covers the vast majority of formats that are produced by modern network cameras. In response to this changing landscape, SecuritySpy now supports the following formats:Īudio: PCM, G.711 (µ-law and a-law), G.726Īudio: PCM, G.711 (µ-law and a-law), G.726, AAC, AMR This method, called RTSP tunnelling or RTSP-over-HTTP, is supported by many network cameras, and I would expect its use to become more dominant especially now it has been endorsed by the ONVIF standard. In response to this, Apple have described a method for tunnelling RTSP data within an HTTP connection, which resolves these issues. ![]() One drawback of RTSP is the fact that it operates on a different port to HTTP (554 compared to 80), and that it is sometimes blocked by proxy servers and firewalls. But now, with improvements in embedded processing capability, and customer demand for more sophisticated and mobile-friendly compression formats, there has been an explosion in MPEG-4-over-RTSP and H.264-over-RTSP implementation in network cameras. For many years, the processing capabilities of network cameras was not good enough to produce the more CPU-intensive compression formats MPEG-4 and H.264, so manufacturers tended to stick to the simplest format with the widest web-browser compatibility, which is JPEG-over-HTTP. Unlike HTTP, RTSP is not limited to carrying just JPEG video data it can conceivably carry video and audio of any compression format.ĭespite the long-standing availability of RTSP as a standard, it has only been relatively recently that it has become widely employed in network cameras. While HTTP is designed for general web content, RTSP is designed specifically for media streaming. This is the primary format upon which SecuritySpy has been built, prior to version 3.0.ġ998 was apparently a good year for video streaming, because it was also the year that the RTSP protocol was invented. HTTP has long been established as a method of transmitting JPEG video streams – based on a data streaming method invented by Netscape in 1998, and since then adopted as an unofficial standard and supported by most web browsers. HTTP is the foundation of communication of the World Wide Web, used for transferring web pages and other associated files between web servers and clients. Using these protocols, it is possible to transmit video and audio in various compression formats (JPEG, MPEG-4, H.264, AAC etc.). There are two main protocols used for carrying video and audio data over IP networks: HTTP and RTSP. The following information about these formats will be useful when making purchasing decisions and setting up video surveillance systems based upon SecuritySpy. The latest version of SecuritySpy supports new streaming formats which significantly enhance compatibility with new and existing network cameras.
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