Configure video encoding
You can configure the video encoding settings for each channel using the Admin panel. Video encoding settings include:
- Video codec: The video codec determines the type of compression and decompression, and also affects the video quality. Options are H.264 (default) and Motion JPEG.
- Hardware or software encoding: Hardware encoding is the default setting and is the recommended encoding for use with Pearl.
- Encoding level: This can be set to High, Main, or Baseline.
- Frame size: The resolution applied to the channel when you stream, record, or output video to a confidence monitor. This can be set to automatically match the input video's resolution or set to a fixed resolution.
- Key frame interval: How often a key frame that contains all the pixels is sent when streaming. The longer the key frame interval, the smaller the video file size (and vice versa).
- Bitrate: If using the H.264 video codec, you can increase or decrease image quality by increasing or decreasing the channel's Bitrate value. Video with a high level of motion and high resolution, such as sporting events, requires a higher bitrate.
By default, Pearl automatically uses the incoming video source frame size as the frame size for streaming and recording when the channel has only one layout with a single video source. If you're channel has multiple video sources or layouts, you must manually set a frame size for the channel.
If you plan to switch layouts during a live stream, a fixed frame rate is recommended. This avoids the stream from stopping and restarting due to frame size changes when switching between single-source layouts that use different frame sizes.
- For optimum system performance, the frame size of the channel should be set to match the frame size of your video input source to avoid scaling, see Optimum CPU performance.
- If you have unchecked all the manual resizing and positioning boxes in the custom layout editor and you downscale the video source using the frame size setting on the Encoding tab (for example, select 1280×720 frame size for a full HD video source), then the source appears cropped within the frame instead of scaling to fit the frame.
- If your channel has a custom layout with only one source and your source and stream aspect ratios differ, then your source appears centered in the frame and matte bars are added automatically to the top and bottom (or left and right sides) of the frame to make up the difference. See Remove black bars (matte) from the video.
- The larger the channel's frame size, the more bandwidth is needed for streaming and the recorded files are bigger. Instead of using the same frame size as the original video source, you can configure a smaller frame size for the channel and let Pearl downscale the video. For example, if the input video signal resolution is 1920×1080 (a 16:9 aspect ratio) and the channel's frame size is set to 1280×720, Pearl downscales the video and streams/records the channel at the lower frame size, using less bandwidth and producing smaller recorded files.
You can add black bars around your video source by adjusting the frame size. For example, if your video source has a 16:9 widescreen/HD format but you need a 4:3 frame size on your output, Pearl automatically adds black bars to the top and bottom of the frame if you choose a frame size for the channel that has a 4:3 aspect ratio.
There is some trade off between video quality and bandwidth size, depending on the encoding settings you choose. The following table lists some additional considerations when choosing video encoding settings.
Video encoding settings
|H.264||H.264 is the default codec and provides high quality video while using low bandwidth. This is the preferred codec for the system.|
|Motion JPEG||This codec is suitable for streaming and recording video, however you get lower quality images and it requires a large amount of bandwidth. Motion JPEG does not support audio.|
|Key frame interval||
The key frame interval feature specifies how often a key frame (a frame that contains all the pixels) is sent when streaming the video. This setting also impacts how quickly a video moves through the frames when a viewer uses the search function of their media player.
Increasing the number of seconds between key frames can significantly reduce your bandwidth and system resource usage with minor impact to your video quality. A good rule of thumb is to keep the interval between 2 to 3 seconds and decrease the key frame interval as the motion increases. Try different settings and note changes in the video quality. If your video quality is poor and jittery you may need to decrease the interval between key frames. If you have unlimited bandwidth and system resources you can choose an option to stream key frames only.
Frame rate reflects the number of images that are encoded per second. Reducing the frame rate for a channel reduces bandwidth usage, and vice versa.
The system's ability to maintain a set frame rate is based on several factors, for example:
When adjusting the frame rate, you may need to try different values to achieve the best outcome.
In general, higher bitrates mean higher image quality, but more bandwidth is needed for streaming and video recordings are larger. If you're using H.264, then you can set the bitrate to improve the image quality.
For example, an HD Blu-ray video is typically in the range of 20 Mbps, whereas a standard-definition DVD is usually 6 Mbps.
If you're unsure what bitrate value to use, start at 5000 kbps (slightly less than a typical DVD) and test to see how this looks for your viewers.
To configure video encoding for a channel:
- Login to the Admin panel as admin, see Connect to Admin panel.
- From the Channel menu, select a channel and click Encoding. The encoding configuration page opens.
- Select a video Codec and do one of the following:
- If JPEG is selected, click Page refresh time and enter a time in seconds.
- If H.264 is selected, select a Video encoding preset and a Video encoding profile.
- Configure the frame size, do the following:
- Uncheck Use current signal resolution as the frame size.
- Select a Frame size from the list of options or enter a custom frame size in pixels.
Enabling Use current signal resolution as the frame size is not recommended if the video input resolution changes frequently. An unstable cable or other disturbance that causes the resolution of the video input signal to change during a live stream can cause the stream to drop. Unchecking this feature helps prevent that.
- Change the Limit frame rate. The default should be adequate in most applications. While decreasing the limit may improve system performance, you may need to test different values to balance video smoothness and processing power
- Change the Bitrate. If using H.264 video codec, you can increase or decrease image quality by increasing or decreasing the target Bitrate value. Video with a high level of motion and high resolution, such as a sporting event, requires a high bitrate.
- Click Apply.
|Video encoding preset||
Hardware Accelerated: This is the default H.264 encoding preset. Choose this setting for best performance.
Software: This matches the default from previous generations of Epiphan products. Only select this if you need software encoding or X.264 encoding to match results created with previous generations of Epiphan products or firmware
|Video encoding profile||
Baseline: Choose this option when streaming to an application that requires robustness and cannot tolerate data loss, for example video-conferencing.
Main: Choose this option for standard-definition broadcasts.
High: This is the default. Choose this option when video is viewed for broadcast and disk storage applications, particularly for high definition television application such as Blu-ray disk storage format and HDTV broadcast service.