Difference between revisions of "Help with Video Encoding"
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When a video doesn't play correctly, it is often because of unusual combinations of these sub-components of the file. For example, a the file's container may claim to contain video written in the AVC (advanced video codec) format, with audio formatted in PCM (pulse-code modulation). But then, the actual audio and video files actually be written in other formats, like IOSM for the video and MP3 for the audio. Often, a computer can scan through all of this information and can try various combinations of audio and video decoders in order to determine a set that work properly, regardless of what the file info says. But web browsers and mobile devices generally don't have the processing power available to do these things, and rely instead on the files being labelled and encoded very precisely according to a specific standards. Into this mix, you can also add the complication that modern standards such as MP4 are actually still evolving and being revised, so many products are not quite caught up to the latest revisions... | When a video doesn't play correctly, it is often because of unusual combinations of these sub-components of the file. For example, a the file's container may claim to contain video written in the AVC (advanced video codec) format, with audio formatted in PCM (pulse-code modulation). But then, the actual audio and video files actually be written in other formats, like IOSM for the video and MP3 for the audio. Often, a computer can scan through all of this information and can try various combinations of audio and video decoders in order to determine a set that work properly, regardless of what the file info says. But web browsers and mobile devices generally don't have the processing power available to do these things, and rely instead on the files being labelled and encoded very precisely according to a specific standards. Into this mix, you can also add the complication that modern standards such as MP4 are actually still evolving and being revised, so many products are not quite caught up to the latest revisions... | ||
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Latest revision as of 17:19, 21 February 2017
Encoding Media
Many formats and techniques exist for compressing, encoding, and packaging audio and visuals into a final video file. A number of different standards exist, and many variations or partial implementations of those standards are out there. This page has suggestions for formatting and tools to ensure that your video file plays correctly on this wiki and in most web browsers.
Tools to encode
On Campus
The following tools are available on campus and can produce files that will work perfectly with all devices.
| Tool Name | Where is it | What to do |
|---|---|---|
| Camtasia Studio (Edit and encode) | All WPI lab, Tech suite, and Loaner Laptop machines | Import Media, Add to timeline, Set video size to "recording dimensions" and then Produce and Share, using the Mp4 Only up to 720p preset. Techsmith's tutorial site: [1] |
| Adobe Media Encoder (Encode) | Library Multimedia Lab, SL 123 Lab, IMGD Labs, Library Anderson Lab B | Drop a video onto the interface, change the preset to H.264, and Press the green play button to start encoding. |
| Adobe Premiere (Edit and Encode) | Library Multimedia Lab, SL 123 Lab, IMGD Labs, Library Anderson Lab B | Start a new project (click Ok on the settings page), File > Import media, Drop a video onto the timeline, and select File > Export > Media. When the Export box comes up, change the Format (dropdown menu) to H.264 and click Export. |
Other
These tools are free, but may require some fiddling to use. They are capable of producing compatible files, but some formats may not work correctly in various circumstances. If you use these tools, test the results!!!
- Zamzar [2]
- Zamzar is free, easy to use, and produces correctly formatted media. Limited to 100 MB files.
- Handbrake [3]
- Handbrake is free and cross platform. It does not always produce correctly formatted files, however.
- VLC [4]
- Primarily a video player, but also able to convert to MP4 (from the Media > Save/convert menu).
- FFMPEG [5]
- The ultimate video converter, but it is a command-line only program. A simple command like this would work for most video files:
- ffmpeg -i inputFile.ext -c:v libx264 -v:b 1000k -c:a copy output.mp4
- However, for some of the more unusual files, a more complex command may be needed
Formatting
Generally, the best video format to use is mp4. The wiki can play other formats including mov, wmv, and flv, but these might not play as reliably. One of the most confusing aspects of video formatting is that the file extension does not always indicate what kind of file your video is. This is because video files are actually containers that contain several files! There's generally some data written into the file that describes the kind of content to expect, and then there are audio and video files packed in, each of which contain their own descriptive data and content.
What makes it all break? When a video doesn't play correctly, it is often because of unusual combinations of these sub-components of the file. For example, a the file's container may claim to contain video written in the AVC (advanced video codec) format, with audio formatted in PCM (pulse-code modulation). But then, the actual audio and video files actually be written in other formats, like IOSM for the video and MP3 for the audio. Often, a computer can scan through all of this information and can try various combinations of audio and video decoders in order to determine a set that work properly, regardless of what the file info says. But web browsers and mobile devices generally don't have the processing power available to do these things, and rely instead on the files being labelled and encoded very precisely according to a specific standards. Into this mix, you can also add the complication that modern standards such as MP4 are actually still evolving and being revised, so many products are not quite caught up to the latest revisions...