Preparing VOD Content for CloudCast™

This is a guide to the formats best-suited for playing Video on Demand (VOD) through the TelVue® CloudCast™ Internet streaming service.

Most online video is encoded using the H.264 video codec and AAC audio codec in an MP4 container. This format is currently the most widely used and will allow your content to be viewed on Android, iOS, Roku, and most web browsers. These video and audio codecs provide high quality without a very high bit rate, making them ideal for streaming over the internet.

The easiest way to prepare content for CloudCast, if you already have a TelVue Broadcast Server, is with a TelVue® Turbo™ Workflow Accelerator, which will automatically encode and transfer your video assets to your CloudCast account.

However, if you are going to prepare your VOD content manually, here are some generally recommended settings for SD and HD videos:

Recommended settings for VOD

SD

HD

Video Codec

H.264; MPEG-4 (Main Profile @ 3.1 Level)

H.264; MPEG-4 (Main Profile @ 3.1 Level)

Video Bit Rate

700-1250 Kbps

2000-2500 Kbps

CBR vs VBR

CBR

CBR

Aspect Ratio

typically 4:3, sometimes 16:9 (widescreen)

16:9 (widescreen)

Resolution

400 x 300 (w/ lower bitrate)

640 x 480 (w/ higher bitrate)

960 x 540 (w/ lower bitrate)

1280 x 720 (w/ higher bitrate)

Image Scanning

Progressive

Progressive

Frame Rate

29.97 or 30

29.97 or 30

Audio Codec

AAC

AAC

Sampling Rate

44.1 kHz

44.1 or 48 kHz

Audio Channels

Stereo for better quality, Mono for smaller filesize

Stereo for better quality, Mono for smaller filesize

Audio Bit Rate

60-84 Kbps

128 Kbps

 

If you want to learn more about these settings, read on…

Video File Format:

If you are exporting your content from a non-linear editor such as Final Cut Pro or Adobe Premiere, H.264 the presets for streaming video that are available should work just fine.

If you need to transcode an existing video, the following programs can encode to H.264:

In many cases custom presets are not required. Many of these programs include presets for Google, YouTube, Apple TV, or other services. Look for these or similar presets under headings like Web Delivery or Online in your program of choice.  If, however, you are prompted to choose your own parameters, here are some basic guidelines:

Bit rate and Resolution:

These are the most important parameters when transcoding video and directly relate to the quality of the viewing experience. A consideration for the widest possible viewing audience should be made – meaning that you should chose a medium to low resolution and bit rate to play well on mobile devices and users without fast connections.

If the recommended settings above do not stream smoothly, you can experiment by changing the resolution and bit rate to lower values.

Variable or Constant Bit Rate:

Most encoders allow you to chose CBR (constant bit rate) or VBR (variable bit rate). VBR will vary the bitrate of the encoding to use more bits per second during high movement / action scenes and lower bits per second with low movement scenes. This provides overall better quality.

However, because these videos will be streamed over the internet, VBR video may cause issues and stuttering in the video (buffering) if the viewer’s device has to suddenly download many more bits per second and doesn’t have the bandwidth to support it. If using VBR, make sure that the “ceiling” or “limit” bit rate is not too high.

Aspect Ratio:

The term “HD” is most commonly paired with a 16:9 aspect ratio, sometimes called widescreen. “SD” usually indicates a 4:3 aspect ratio.

Most source video these days is in the HD ratio of 16:9.  If you have older SD videos in 4:3 aspect ratio, make sure the transcoding process does not “stretch” the final video if exporting to HD 16:9.  When transcoding source content that is 16:9 into 4:3 container, “pillarboxes” – black bars on either side of the video – are typically added.  When transcoding source content that is 4:3 into a 16:9 container, the content is usually “letterboxed”.

Image Scanning:

For online video, always encode with progressive scanning, not interlaced.  This is the meaning of the ‘i’ or the ‘p’ in the resolution measurement (e.g., 1080p for HD video).

The difference is:

  1. Interlaced: Traditional television or video display, where half the picture appears on the screen at a time and the other half follows an instant later.  This scanning method uses odd then even lines that combine to produce an interlaced frame.  The problem for VOD is that not all video players will de-interlace the video.

  2. Progressive: The entire picture is painted at once, all line fields appear on the screen at the same time.  This scanning method uses both odd and even lines in a progressive path (one-after-the-other) to produce a progressive frame.

Frame Rate:

Frame rate is often set by your non-linear editing based on the file format you choose. For H.264 and MPEG-4, the default is 29.97 FPS, the NTSC standard. 30 FPS is also very commonly used in video streamed over the internet.

Audio File Format:

For H.264 and MPEG-4, the default and recommended audio format is AAC.  it a very advanced codec that achieves high quality with low bit rates.

Audio Sampling Rate:

For H.264 and MPEG-4, the default sampling rate is 44.1kHz.   48 kHz is the standard audio sampling rate used by professional digital video equipment such as tape recorders, video servers, vision mixers, etc.

Audio Channels:

While Mono offers a smaller file size, Stereo offers more optimal playback with two distinct audio channels. If your source only has one channel of sound, there’s little reason to then transcode it to stereo sound. But if your source was recorded with stereo sound, most people would opt to retain those distinct audio channels and transcode with stereo sound.

Audio Bit rate/ Data Rate:

Similar to video bit rate, this corresponds to the quality of the audio. AAC (advanced audio codec) can achieve better quality sound compared with MP3 at the same bit rate.

• Common bit rates

  1. SD: 32 Kbps-96 Kbps

  2. HD: 128 Kbps-192 Kbps

Passes:

Some encoders allow you to perform “2-pass” encoding on VOD content. While each encoder will have a slightly different interpretation of what this means, 2-pass encoding typically means that the encoder will first scan the video once to determine the optimal encoding method, and then actually perform the encoding on the second pass. This is typically paired with variable bit rate encodings, so that the encoder has better anticipation of when it needs to increase and decrease the bit rate.

Note that 2-pass encoding will take longer than 1-pass, and may not provide a dramatic improvement to quality.


These recommendations are for Video-on-Demand (VOD) delivery through TelVue CloudCast.  Live streaming through TelVue CloudCast entails a different process, with different encoding requirements.

To find out how to stream a live channel with TelVue CloudCast, please contact sales@telvue.com or call 800-885-8886 for more information.

 

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One Comment

  1. If material has been recorded at 23.98 what is the best frame rate for vod on telvue