Live Streaming Basics
Oct 19, 2011 4:22 PM, Provided by Digital Rapids
Expanding a ministry’s reach through live video streaming.
There are a number of subtleties that can cause issues for those first starting streaming.
1. Upload vs. download speeds of Internet connections
The upload speeds are typically much lower, but many people don’t realize that.
2. Using the same Internet connection for streaming that is used for other church tasks that may be going on at the same time.
3. A misconception we hear occasionally is that if you’re just create a small, low-bit-rate output for the Web or mobile phones, you can get away with using a lower-quality source signal (e.g. “noisy” video, lower-quality connections, etc.). In fact, the opposite is true—low-quality sources have a lot of video noise, etc., that makes the video harder to compress, and you’re wasting bits compressing the junk in addition to the content. In a low-bit-rate output, those wasted bits are a higher percentage of the total, so you can end up with a LOT lower quality output than if the source had been “clean”. You should always use the best quality signal possible, starting at the camera itself—lower-end cameras can introduce noise into the video signal, and lighting is also a big factor in compression quality. Video shot in low light has considerably more video noise than well-lit video; low-light video that looks OK on a monitor connected directly to the camera can look considerably worse once compressed for streaming. For connectivity, SDI digital signals are ideal. For analog video, component signals are the best, followed by Y/C and composite. The best encoding/streaming hardware cards and systems can also do a lot to help “clean up” the video. For example, the Digital Rapids hardware cards that all of its solutions are built on feature advanced video preprocessing, which grooms the input signal to be more compression friendly by removing video noise, providing higher-quality de-interlacing than software algorithms typically allow, and more. The result is that such systems can produce high-quality output even when the input signal is less than ideal but fantastic quality with a good source.
4. There’s a trade-off between visual quality and your choices of resolution and bit rate. A common mistake is to decide to stream at higher resolution (frame size) with the expectation that it will provide better quality (just like high-definition television is better quality than standard-definition). The problem is that a larger size requires more compression to get down to a specific bit rate; so the resulting visual quality may be much lower than smaller size at same bit rate. A visual example is useful: As you can see from the example images, particularly with low bit rates, streaming at a lower resolution can actually give better quality than streaming at higher resolution at the same bit rate. If you want to increase your resolution, you likely need to use a higher bit rate to accommodate it.
5. That leads to another possible mistake, though: choosing too high a bit rate. As discussed earlier, the church’s Internet connection must be fast enough to deliver streams at your chosen bit rate. Even if the church’s connection is fast enough, however, you need to make sure that the bit rate isn’t too high for your viewers. If your bit rate exceeds the sustainable bandwidth of a viewer, it’s likely to result in an unwatchable experience (lots of buffering, stuttering, skipping, etc.). Be sure to offer a stream with low enough bit rate for the “minimum” connection you expect of your viewers. In fact, it may be best to consider offering streams at multiple bit rates—at least one for those with slow connections, and a high-quality stream for those with fast connections. Some encoders, such as Digital Rapids’ TouchStream and StreamZ, can output multiple streams at various resolutions and bit rates simultaneously from the same source signal. But remember that if the church is offering a choice of multiple streams, its Internet connection must be fast enough to send those streams out together—at least as fast as the sum of the bit rates of the streams. For example, if you’re offering a 384Kbps stream and a 768Kbps stream, your outgoing Internet connection must be at least 1152Kbps.
6. Last but not least, don’t forget that even though your streams aren’t Hollywood blockbusters or paid commercial programming, video quality likely still matters to your audience. As technology has advanced, audience expectations have also increased. And it’s much easier for a viewer to focus on the message when they aren’t distracted by quality issues in the delivery mechanism (video).
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