# H.264,MPEG-4 format
# 1920x1080 resolution (for HD1080p)
# 44.1KHz Stereo MP3 or AAC audio
# Frame rate as the original video
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How to upload widescreen videos
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Originals, Please! - The less a video is re-encoded prior to uploading, the better the resulting YouTube video quality. We encourage you to upload your videos as close to the original source format as possible, with a minimum of intermediate re-encoding steps. Each re-encoding can generally degrade the quality of your video and may create some specific problems which we'll address below.
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Frame Rate - The video frame-rate should be the same as the original where possible. For film sources, a 24 fps or 25 fps progressive master yields the best results, while videos that have had a re-sampling transfer process applied — i.e. a Telecine pulldown — often result in a lower quality video.
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Resolution - High-definition videos are the preferred format for ingestion which result in YouTube videos of the highest quality currently available. It also means your video can be upgraded as new formats are developed on the site.
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Testing - Since there is no facility to re-upload videos, it's important to test that your audio and video quality are satisfactory before you release your video publicly onto YouTube.
Once a video becomes popular, the number of views, user ratings, user comments and other community data, cannot be transferred if another, higher quality version of the same video is uploaded. Make sure you get it right!
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Aspect Ratio - The aspect ratio of the original source video should always be maintained when it's uploaded: Uploaded videos should never include letterboxing or pillarboxing bars.
The YouTube player automatically adds black bars so that videos are displayed correctly without cropping or stretching, no matter the size of the video or the player. For example, the player will automatically add vertical bars (pillarboxing) to 4:3 videos in the new 16:9 widescreen player size. If the player is re-sized (i.e. when embedded on another website), the same process takes place so that 16:9 videos are letterboxed (black bars top and bottom) when the player is sized to 4:3. Similarly, anamorphic videos will be automatically letterboxed when shown in either 16:9 or 4:3 sized players. The player can only do this if the native aspect ratio of the video is maintained.
If letterboxing is added to a video before it is uploaded (i.e. in the case of creating a 4:3 video from a 16:9 master), the widescreen player will add pillarbox bars too, resulting in black bars all around the video (windowboxing) and a bad viewing experience (see the diagram below).