Standalone VGA Grid User Guide
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Configure encoding

You can modify the encoding settings for each channel you create. These settings let you perfect your stream by selecting the right frame size, bit rate, audio/video codecs and more.

This section covers the following encoding topics:

Configure video codec

To configure encoding:

  1. Login to the Admin panel as admin. See Connect to the Admin panel.
  1. Click the Encoding link for your channel; the encoding configuration page opens.

  1. Click the Codec drop-down menu to change the size and speed of the compression and decompression and the quality of the image. Choose one of the following options from the Codec drop-down menu.

ValueDescription
H.264H.264 is the default value and provides high quality video while using low bandwidth. This is the preferred codec for the system.
Motion JPEGThis is suitable for live streaming and video, however may have low quality images while using high bandwidth. Motion JPEG does not support audio.
MPEG-4

This may be suitable for presentations. Provides good image quality, while using moderate bandwidth.

  1. If the selected codec is Motion JPEG, you can configure the Page refresh time. Specify a time in a seconds.
  1. If the selected codec is H.264 (default), click Video encoding preset to define how the video stream is encoded. Choose one of the following:
ValueDescription
Hardware
Accelerated
This is the default H.264 encoding preset. Choose this setting for best performance.
SoftwareThis matches the default from previous generations of Epiphan products. Choose this only if you need software encoding or X.264 encoding to match results created with previous generations of Epiphan products or firmware.
  1. If the selected codec is H.264 (default), click Video encoding profile to limit or include video formats that are supported. Choose one of the following:

ValueDescription
BaselineChoose this option when streaming to an application that requires robustness and cannot tolerate data loss, for example video-conferencing.
MainChoose this option for standard-definition broadcasts. This is the default.
HighChoose 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.

Video encoding profile and preset can be set only when the H.264 codec is selected.

  1. If all your changes are complete, scroll to the bottom of the page and click Apply.

Configure frame size

By default, for channels with only one layout and when that layout has only one video source, your Standalone VGA Grid automatically uses the incoming source frame size as the stream frame size. Frame size greatly affects the amount of bandwidth needed to transmit your stream. The larger the frame size, the more bandwidth you need to stream it. So you may want to keep the frame size the same as your source, or you may want to apply upscaling, downscaling, stretching, or black bar framing, depending on your needs.

For example:

  • if the input signal resolution is 1920×1080 (a 16:9 aspect ratio)
  • and stream frame size is set to another 16:9 frame size such as 1280×720,

the smaller stream frame size causes the system to downscale the image and use less bandwidth to transmit.

Or if you have a widescreen/HD format source but need a 4:3 output frame size, you can add black bars to the top and bottom of the frame.

The system is designed to provide scaling, however for the best overall system performance (particualrly when reaching maximum system capacity), configure your source to provide the correct frame size and avoid scaling.

To configure your stream's frame size:

  1. Login to the Admin panel as admin. See Connect to the Admin panel.
  1. Click Encoding for the your channel; the encoding configuration page opens.
  2. Scroll to the Frame size section.
  3.  Perform one of the following steps:

    Using current signal resolution as the frame size only works for channel layouts with a single source. If you're using multiple sources, follow the steps below to set your frame size.

    1. Check the Use current signal resolution as the frame size check box. Enabling this feature greys out the other frame-size configuration fields. The system automatically streams at the frame size of the input signal. 

    If you change the frame size (resolution) of the input signal after streaming (or recording) begins your may see interrupted streaming and recording. Enabling this feature is not recommended for systems where input resolution is changed frequently.

    1. Change the frame size, follow the steps below.
  4. Set the Frame size values to reflect the dimensions required for your stream. Some suggested values cover popular resolutions of cameras and display devices such as monitors, but you may also specify something custom:

    1. Uncheck Use current signal resolution as frame size.
    2. Type a frame size in the field; or
    3. Select an option from the sizes shown, the dimensions will appear in the frame size field.

Scaling occurs automatically (no extra configuration needed) when you make the dimensions larger, smaller, or a different aspect ratio than the source.

If your channel has a layout with only one source and your source and stream aspect ratios differ, when viewing that layout, your source is centered in the frame and matte bars are added to the top and bottom or left and right sides to make up the difference. See Remove black bars (matte) from the video.

  1. If all your changes are complete, scroll to the bottom of the page and click Apply.

If you plan to use layout switching during a live stream, it's best to choose a fixed layout size. This avoids causing the stream restart due to frame size change when you switch between single-source layouts that use frame sizes.

Fine tune stream settings

Along with video/audio codecs and frame size, there are other configurable stream settings that affect quality and bandwidth. Like with frame size selection, values for these settings can be a tradeoff between bandwidth available and quality for stream viewers.

A table at the end of this section provides additional guidance for the settings

To fine tune your stream's settings :

  1. Login to the Admin panel as admin. See Connect to the Admin panel.
  1. Click Encoding for your channel; the encoding configuration page opens.
  2. Scroll to the Key frame interval setting.
  3. Click the Key frame interval drop-down box to choose how often a key frame (a frame that contains all the pixels) is sent when streaming the video. The longer the key frame interval the smaller the video file size, and vice versa.
  1. If desired, 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.
  2. If using H.264 of MPEG4 video codecs, 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.
  3. If all your changes are complete, scroll to the bottom of the page and click Apply.

Stream settings guidance

SettingDescription
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

Frame rate reflects the number of images captured by the device per second. Reducing the frame rate reduces bandwidth usage, and vice versa.

The system's ability to maintain a set frame rate is based on several factors, for example:

  • overall system load affects the ability for the device to process pixels;
  • available network bandwidth;
  • the source and stream frame size (resolution);
  • the type of motion that is captured; and
  • number of users accessing the stream.

When adjusting the frame rate, you may need to try different values to achieve the best outcome.

Bitrate

In general, higher bitrate mean higher image quality in the stream, at the cost of higher bandwidth needed to transmit it.

For comparison against something you are likely familiar with, an HD Blu-ray video is typically in the range of 20 mbps, standard-definition DVD is usually 6 mbps.

If you don't know what value to use, a good place to start is 5000 kbps (slightly less than a typical DVD). Test to see how this works for your viewers and adjust.

 

Configure audio codec

If your channel sources included audio (see Create a simple channel or Create a custom channel), your stream will by default use the AAC audio codec at 48 kHz. You can modify this setting to best match your streaming or post-processing needs.

To configure your stream's audio codec :

  1. Login to the Admin panel as admin. See Connect to the Admin panel.
  1. Click Encoding for the your channel; the encoding configuration page opens.
  2. Scroll to the Audio settings section.

  1. Ensure the Enable audio checkbox is checked.
  1. If the default audio format AAC 44KHz, stereo, 320 Kbps is not desired, click the Audio format drop-down menu to select an audio codec. A table at the end of this procedure gives details about each option.
  2. Click the Audio channels drop-down menu to choose mono (1 channel) or stereo (2 channels).

If desired, you can choose Mono to have left and right stereo channels combined and streamed together (i.e. when listening to the streamed audio, the same blended sound will come through both the left and right channels).

  1. Select an Audio bitrate from the drop-down menu. The table at the end of this procedure gives some guidance on audio bitrates.

For stereo audio, we recommend 256 kbps or 320 kbps.

  1. If all your changes are complete, scroll to the bottom of the page and click Apply.

Audio codecs and bitrate guidance

ValueDescription
AAC

AAC is the default audio codec.

This codec is comparable to MP3, and may have better sound quality with a similar bit rate. Supported values are 16, 22, 44 and 48K kHz. Most digital signals (HDMI or SDI sources) use 48 kHz audio.

Matching the encoded level with the source level provides the best sound quality by avoiding audio resampling. For analog signals, 44 kHz provides higher sampling.

The maximum bitrate for mono encoding of a 44 kHz signal is 264 kbps. For stereo, 320 kbps is supported. Note that lower bitrates (e.g. 32 kbps) with a 44 kHz signal may result in distorted audio.

MP3

MP3 provides a common audio format for audio storage.

Supported values are 22 kHz, 44 kHz and 48 kHz. Most digital signals (HDMI or SDI sources) use 48 kHz audio. Matching the encoded level with the source level provides the best sound quality by avoiding audio resampling. For analog signals, 44 kHz provides higher sampling.

Flash (FLV) doesn't support 48 kHz MP3 audio. When selecting this value you'll need to use a media player (or install ASF browser plugins) to preview your channel.

PCM

Pulse Code Modulation (PCM) is a standard for digital audio in computer and other devices such as, digital telephone systems.

Most digital signals (HDMI or SDI sources) use 48 kHz audio. Matching the encoded level with the source level provides the best sound quality by avoiding audio resampling. For analog signals, 44 kHz provides higher sampling.

Flash (FLV) doesn't support 48 kHz PCM audio. When selecting this value you'll need to use a media player (or install ASF browser plugins) to preview your channel.

Codec and file format compatibility

Not all streaming and recording protocols support all combinations of video and audio codecs. Use the tables below to determine what settings work for your streaming and recording needs.

The following table displays the compatibility between the video/audio codecs and formats supported for streaming.

Video Codec selectedAudio Codec selectedRTSPFLVASFMPEG-TS
H.264No audio codecüüüü
H.264PCMüüü 
H.264MP3üüüü
H.264AACüüüü
MPEG-4No audio codec  ü 
MPEG-4PCM  ü 
MPEG-4MP3  ü 
MPEG-4AAC  ü 

The following table displays the compatibility between the video/audio codecs and formats supported for recording.

Video Codec selectedAudio Codec selectedMP4 and MP4-FragmentedAVIMOV
H.264No audio codecüüü
H.264PCMüüü
H.264MP3üüü
H.264AACüüü
MPEG-4No audio codecüüü
MPEG-4LPCMüüü
MPEG-4MP3üüü
MPEG-4AACüüü