Unlike digital photos, which are predominantly in JPEG format, there isn't a single common standard for videos. However, virtually everything - including smartphones and tablets - can play MP4 videos, and this is currently the most common format.
If you have a video, perhaps from your camcorder, digital camera or something you downloaded, that's not compatible with your phone, tablet or TV, here's how to convert that video to MP4.
How to convert a video to MP4 and other formats
Changing a video's format is easy with the right software. Fortunately, there are plenty of free apps which will do this for you. Some are easier to use than others, and some have more features such as cutting out sections, dealing with multiple audio tracks (for different languages, say) and subtitles.
To keep things simple, most allow you to choose your device, such as an iPhone, rather than asking you to pick the correct settings. However, the MP4 format is a safe choice for practically all modern devices because iPhones, Android phones and TVs will play MP4s.
If you already have some video editing software, this will be able to import video in a variety of formats and export to MP4. Obviously, you'll also be able to edit the video if you need to as well. Here are the best free video editors
There are plenty of free and paid-for video converters and they all work in a similar way. Free tools usually add on a pre-roll or post-roll advertising the software, while some will watermark your entire video or limit you to a certain length.
Best free video converters
Freemake is easy to use, but we've had mixed results over the years. Converted videos occasionally had out-of-synch audio or corruption across the bottom edge. At other times, they're fine. Plus, Freemake supports nVidia Cuda so if you have a compatible graphics card, the conversion process can be hugely speeded up.
It's not amazingly quick, but it does a reliable job and is fairly easy to use.
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Another popular free option. This has always been reliable, but lacks an easy-to-use interface, especially if you want to convert several videos at once. But it does the job and is good if you want to delve into framerates and bitrates.
This is a limited free version of a paid-for product, and won't let you output videos in 1080p or 4K. There's no batch conversion either - those features are only in the PRO version.
Paid-for video converters
Paid-for converters such as MediaEspresso (which costs £35) don't watermark or add splashes to your video. MediaEspresso also includes support for Intel Quick Sync, nVidia Cuda and AMD APP to vastly speed up the conversion process. and can convert photos and music into the bargain.
How to convert a video to MP4 step by step
The process is similar with all converters but we're using Freemake here. Essentially you select the video you want to convert, choose a device preset or video format, give it a filename and location for the converted video and press the 'Convert' button.
Depending on the length of the video and your hardware, the conversion could take anything from a few seconds to many hours to complete.
Step 1: Download Freemake and then choose Custom installation when given the choice. Deselect the optional software when prompted, because Freemake is bundled with extra stuff that gets installed if you choose the automatic installation.
Step 2: Launch the app when prompted and click the + Video button and navigate to the video you want to convert. We've chosen an .AVI file.
Step 3: Click the 'to MP4" button at the bottom. You will see a window like the one below. You can click the ... button to choose a name and location to save the converted video. By default, it will use the same folder as the source video.
Step 4: At this point you can click the blue Convert button. But if you want to make any changes to the video, you can click the blue cog icon near the top to see a screen like this:
This allows you to change the resolution, video codec (see the next page for an explanation) plus other settings.
Click OK, the Convert to convert the video to MP4.
Understanding video formats
Using presets is great if you don't know what you're doing. But using them might result in poor video quality, or you might end up with files that are too big, and use up a lot of your phone's storage. Once you understand things such as resolution and bitrate, you'll be able to set your video converter manually and get better results.
Resolution
If you're converting video from an HD source, such as a camcorder, you'll start with a big, high-quality file. Let's say you want to watch that video on your smartphone. There's little point in retaining the video's full HD resolution of 1920x1080, even if your phone can play it.
Smartphones with 1920x1080 screens exist, but most have lower resolutions. In your video converter, enter the resolution of your phone's screen. This will reduce the size of the resulting video file, and it should also make it look better on your phone, as well as saving the phone from having to downscale the video to fit.
Aspect ratio
This brings us neatly to aspect ratio. 1080p video (that's video with 1080 horizontal lines) tends to have an aspect ratio of 16:9. Divide 16 by 9 and you get 1.77, which is the same as dividing 1920 by 1080. To find your phone's aspect ratio, divide the resolution of its longest size by its shorter side.
For the Samsung Galaxy S3, that's 1280 / 720. Again, it's 1.77. For the iPhone 4S, it's 960 / 640 = 1.5.
When your converted video has a different aspect ratio to the original, you either lose information (chopping off the sides or top and bottom) or gain black bars at the sides or top and bottom.
Each video converter is different, but it should give you the option of how to handle an aspect ratio change.
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Framerate
This is the number of video frames captured or displayed per second. In the UK, we have a standard (PAL) which is 25fps (frames per second). Movies use video with 24fps. We'd advise leaving the framerate alone, unless your device can't play the video at its original frame rate. The original Apple TV, for example, is limited to playing 720p video (1280x720 resolution) at 24fps.
Container
Codec and container are two frequently confused terms. One reason for this is that the codec and container can share the same name, such as MP4 (MPEG-4).
Put simply, the container is a way of packaging the audio and video together in one file. You can think of it like a zip file which can hold several files of different formats. Examples of containers include: .MP4, .MKV, .AVI, .MOV, .OGG, .ASF.
Codec
Within a video container is an audio file and a video file. A codec describes the method by which each has been compressed.
For example, an .AVI container might contain DivX video and MP3 audio files. An .MP4 file might contain MPEG-4 video and AAC audio. One of the most popular containers for HD video is .MKV, which can include H.264 video and AAC audio. But the latest is H.265 which is used for most 4K video as it's much more efficient that H.264 and results in smaller files without a loss in quality. It's also used to broadcast 4K video and virtually all 4K TVs support it.
For the vast majority of uses, including for Android and iOS devices, the MPEG-4 video codec is best. To be specific, H.264 (also known as MPEG-4 AVC) is the most efficient rather than plain MPEG-4, so you'll get the best image quality for the smallest file size by choosing H.264. Video converters sometimes call it x264.
Bitrate
The video and audio within a container file have their own bitrates. Bitrate is a measurement of the number of bits that are transmitted over a set period of time. The bottom line is that the more bits in your video, the higher quality the image.
For video, bitrate is usually expressed in Mbps - megabits per second. Blu-ray discs typically have a bitrate of between 20 and 30Mbps. That's way too high for a smartphone or tablet, where you can get away with perhaps only 2-5Mbps.
Bitrate is related to file size - you can calculate the expected file size by multiplying the bitrate by the video's duration. Don't forget to add the bitrate and duration of the audio as well. Audio bitrate is much less than video, and is typically less than 320Kbps (kilobits per second). 1Mbps = 1,000Kbps.
You'll have to experiment with bitrate to find the optimum setting for your device. Set it too low and you'll end up with a nice small file, but poor quality - especially when there's a lot of movement on screen.
Constant vs. variable bitrate
Making matters more complicated, you can opt for a fixed or variable bitrate. With variable bitrate, you may (or may not, depending on your video converter) be able to set a minimum and maximum bitrate. The encoder then tries to compress the video as efficiently as possible, using the minimum bitrate when there's little or no movement, and the maximum when there's movement in the entire frame.
The advantage is that you should get better quality video with a smaller file size, but variable bit rate isn't usually the best option if you're streaming the video across the internet.
Fixed bit rate means the bitrate is constant throughout the video. This usually gives smoother playback, at the expense of a larger file.
Again, you may have to experiment to see what works best on the device on which you're playing the video.
If you're unsure about the video specifications for your device, look in the user manual or search online to find them.
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