Showing posts with label AXIS. Show all posts
Showing posts with label AXIS. Show all posts

Sunday, September 11, 2011

IP cameras with Audio Detection

What is the best IP cameras with audio you used?
What security audio and video applications have you had experience with and what is the best IP cameras with audio you used?
What is IP Camera Audio and Advanced Audio Detection?
-- Many More Question comeout in my mail/phones ...

If you’ve never considered having an audio component with your surveillance system that may be because analog CCTV systms require separate audio and video cables to be installed from end to end which becomes difficult and costly over long distances. IP cameras make the implementation of audio a lot simpler because the audio and video information are sent over the same network cable eliminating the need for extra cabling.

More and more IP camera audio is becoming a common feature not only because it’s easier to process over a network cable but also because the importance of this additional surveillance medium is now being recognized.

Importance of IP Camera Audio:

Detect emergency situations and make sense of other events.
Audio covers a 360° area - surveillance systems coverage is extended beyond the field of view.
Audio detection can trigger email or, other alerts and automatically direct where a camera should record.
Having audio integrated into your surveillance simply gives you more information about a situation. Many times something is brought to our attention first by what we hear, not what we see. Car alarms, gunshots, breaking glass, and screams will not be recognized by a surveillance camera without audio. With 360° coverage, an event happening behind a camera can still be detected.

Three Audio Modes
If you’re considering audio for your appliction your intended use should be clear because it can affect which IP cameras you can select as there are three audio modes available:
Simplex: Audio can be sent in one direction only. Either from the camera only (most likely) or, from the user only.
Half-Duplex: Audio can be sent and received in both directions (to/from camera and user), BUT only in one direction at a time.
Full-Duplex: Audio is sent and received at the same time - similar to a telephone conversation.
For example, Axis offers a camera, the Axis 207MW that offers one-way audio with a built in mic while the Axis M1054 offers two-way audio support with a built-in mic and speaker.
Features such as noise cancellation and echo cancellation are also available that reduce background noise or eliminate feedback.

Audio Detection Alarm
In the same way that an IP camera can analyze video, they can intelligently analyze audio as well. As noted above, audio can hear what the video cannot see. Audio detection complements video motion detection very well because it reacts to events in areas that are too dark for the video motion detector to pick up on.
Audio detection alarms can be programmed so that when any sound (glass breaking, voices in a room, etc.) is detected, they can trigger an IP camera to:
Send & record video and audio
Send email or other alerts
Active external devices - Alarms, floodlights
Trigger a PTZ IP camera to automatically pan to a preset location to begin recording.
Audio detection can be enabled all time, at specific times, or disabled. It can also be configured to trigger an event if a sound level rises above, falls below, or passes a certain level of sound intensity. Sony IP Cameras has a great video demonstration of this function here:
Some of the applicable Sony IP cameras and video servers that have this feature can be found here:
Sony SNC-CH140
Sony SNC-RS46N
Sony SNT-EX101

Audio Compression & Audio Bit Rates:
Audio compression and audio bit rates, just like video compression and video bit rates, are an important consideration when calculating total bandwidth and storage requirements.
Just like video, audio compression uses a codec to reduce the size for efficient transmission and storage. Some audio codecs support CBR (constant bit rate) mode only or both CBR and VBR (variable bit rate) - these factors affect quality and file size.
Bit rate is an important audio setting because it determines the level of compression or, quality of the audio. Generally speaking, the higher the compression level = the lower the bit rate = the lower the audio quality.

Audio/Video Synchronization
Audio and video are two separate packet (data) streams that are sent over a network. For audio and video to play back perfectly syncronized, the two packets must be time-stamped so that they match up.

Best Practices For Audio Implementation
Audio Equipment & Placement: Select a location that will minimize interferring noise and one that’s as close to the source of the sound as possible.
Amplify Audio Signal Early: This minimizes noise in the signal chain.
Acoustical Adjustments: Adjust input gain and use features such as echo cancellation to improve audio quality.
Codec & Bit Rate Selection: Codec and Bit Rate choice affect audio quality. High compression = low quality (but available bandwidth may be a deciding factor).
Shielded Cable: Shielded cable reduces disturbance and noise. Avoid running cable near power cables or high-frequency switching signals.
Legal Implications: What are you allowed to record? Some countries restrict the use of audio and video surveillance - be sure to check with your local authorities.

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Saturday, August 13, 2011

Which Image Quality is Better

When thinking about maximizing image quality, resolution is usually the first thing that comes to mind. However, resolution is not the only factor that impacts quality. The amount of bandwidth available and used can have a dramatic impact on image quality. In this report, we examine bandwidth and the effect that it has on quality across numerous cameras.
Which Image Quality is Better?
To better understand image quality, let's start by examining two samples of the same scene side by side:
 
Consider two questions:
1. Which camera has higher resolution? A or B?
2. Which camera is better? A or B?
It is pretty obvious that the image from Camera B is better so this should be a simple case.
The reality is that those images are from the same camera at the same resolution and frame rate (720p/30). All that was done to the camera was changing the Constant Bit Rate target from 512 Kb/s to 8 Mb/s.
Factors Impacting Quality:
Even with the same resolution, two common settings impact quality: 
1. Bit Rate: Most cameras can have their bit rate adjusted to specific levels (e.g., 512 Kb/s, 2 Mb/s, 8Mb/s, etc.) 
2. Quantization Level: Most cameras can have the level of compression adjusted (often called a quality or compression setting with options from 1-10 or 0-100)
Typically, these are mutually exclusive. If you lock in bit rate, the camera will automatically adjust the quantization level to not exceed the bandwidth set. Vice versa, if you set the quantization level, the camera will automatically change the bandwidth consumed to make sure the quality / compression always stays at the same level.
Our Test Process
We wanted to better understand how changes in these two factors impact video quality. To do so, we did a series of tests with three HD cameras: the Axis P1344, the Sony CH140 and the Bosch NBN-921.
For the bandwidth tests, we tested each camera at the following levels:
  • 512 Kb/s
  • 1 Mb/s
  • 2 Mb/s
  • 4 Mb/s
  • 8 Mb/s
We did this across a series of scenes to see how quality would vary in different conditions:
  • Daytime Indoors (300 lux)
  • Nighttime Indoors (.5 lux)
  • Daytime Intersection
Finally, we did a similar series of tests varying the quality level of a VBR camera (the Axis across 0, 30, 60 and 100 levels) to better understand changes in quality and bandwidth consumption.