Difference between revisions of "Digital Movie Caveats"
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== PAL Speedup == | == PAL Speedup == | ||
| − | When a 2 hour movie plays in 1 hour 55 minutes, and all of the actors voices are slightly higher in pitch, it tends to go unnoticed by the average collector. This problem is caused by [[PAL Speedup]]. Once you become aware of it, you will never be able to ignore it. Videos with PAL Speedup should be marked as bad and not kept in your collection. | + | When a 2 hour movie plays in 1 hour 55 minutes, and all of the actors voices are slightly higher in pitch, it tends to go unnoticed by the average collector. This problem is caused by [[PAL Speedup]]. It is an increase of 4.2% in pitch and speed that results from the conversion of film (or NTSC television) to the European PAL format. The 25fps PAL version of the movie ends sooner than it should because it played too fast. Once you become aware of it, you will never be able to ignore it. Videos with PAL Speedup should be marked as bad and not kept in your collection. Avoid video files of American films that have been converted to PAL (25fps.) |
* See Section: [[PAL Speedup]] | * See Section: [[PAL Speedup]] | ||
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The actors appear short and fat, or strangely tall and thin, because the image is stretched either vertically or horizontally. Sometimes an incorrect aspect ratio is caused by a video mastered from a European source converted to the North American standard, and other times the person creating the video simply did not use the correct settings in the encoding software. Video players such as [[VideoLAN Player]] can override the incorrect aspect ratio thus making the video appear correct for that particular viewing. However, with some media devices the problem cannot be corrected. Aspect ratio can sometimes be corrected by modification of the video header, depending on the encoding used. | The actors appear short and fat, or strangely tall and thin, because the image is stretched either vertically or horizontally. Sometimes an incorrect aspect ratio is caused by a video mastered from a European source converted to the North American standard, and other times the person creating the video simply did not use the correct settings in the encoding software. Video players such as [[VideoLAN Player]] can override the incorrect aspect ratio thus making the video appear correct for that particular viewing. However, with some media devices the problem cannot be corrected. Aspect ratio can sometimes be corrected by modification of the video header, depending on the encoding used. | ||
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| + | [[Cinema Aspect Ratios]] from the video source should be preserved. Since most modern Blu-ray movies are released in 2.39:1 aspect ratio, you get bars across the top and bottom of the screen when viewing on your home 16:9 LCD television. This is fine and preferred over stretching the image during encoding. Stream and container mismatches also result in aspect ratio problems. One common mismatch is a 2.37:1 stream using a 1.78:1 container. | ||
Related to video with an incorrect aspect ratio are problems such as over-cropping and capture of the black area in letterbox source. These are also issues to be aware of. | Related to video with an incorrect aspect ratio are problems such as over-cropping and capture of the black area in letterbox source. These are also issues to be aware of. | ||
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== Over Encoding == | == Over Encoding == | ||
| − | If you see a 2 hour video that is 4 GB in size or larger, it is over encoded. There is more bit information captured than what is necessary. Even if you have a 74" wide screen high definition television you are not going to be able to discern the quality difference in a properly encoded H.264 that is 1.2 GB in size compared to an over encoded 4.6 GB video. Furthermore, a 720p is better than a 1080i. For a 2 hour movie at 720p in H.264 with a file size of just under 1GB the quality is going to be superior to a store bought DVD. If you feel you need 1080 make sure it is progressive scan and not interlace (1080i) and look for one that is re-encoded using H.264 with a file size around 2GB for a 2 hour video. Anything more is just a waste of bandwidth and hard drive space. Even if hard drive space is cheap, why be inefficient? Also, for a LAN video server that streams to mobile devices, the 720p video files are much easier to digest. | + | If you see a 2 hour video that is 4 GB in size or larger in [[H.264]], it is over encoded. There is more bit information captured than what is necessary. Even if you have a 74" wide screen high definition television you are not going to be able to discern the quality difference in a properly encoded H.264 that is 1.2 GB in size compared to an over encoded 4.6 GB video. Furthermore, a 720p video is better than a 1080i. For a 2 hour movie at 720p in H.264 with a file size of just under 1GB, the quality is going to be superior to a store bought DVD. If you feel you need 1080 HDTV video make sure it is progressive scan (1080p) and not interlace (1080i) and look for one that is re-encoded using H.264 with a file size around 2GB for a 2 hour video. Anything more is just a waste of bandwidth and hard drive space. Even if hard drive space is cheap, why be inefficient? Also, for a LAN video server that streams to mobile devices, the 720p video files are much easier to digest. |
| + | The [[H.264]] codec is great at creating highly compressed video with excellent quality. That is what the codec is for. You are not taking advantage of H.264 if you have a nearly uncompressed video. With older codecs such as XviD, quality loss is noticeable, yet not terrible, when trying to achieve file sizes at around 800mb for a 2 hour movie with a 720p source. No quality loss is noticeable by the human eye when doing the same using [[H.264]]. Even more interesting is the fact that the more you compress a video in H.264 the better the codec works, up to a point. Finally, quality cannot be added back. When someone creates a video file at 1080p but used a DVD source, they are creating unnecessary replicated pixels with no additional quality. The file is huge when it is unnecessary. | ||
| + | Look for properly compressed H.264 video with reasonable file sizes appropriate for the length of the video. | ||
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Latest revision as of 21:44, 14 July 2014
For people collecting digital movies, this is a quick guide to help you avoid some of the poor quality stuff out there. The digital video files available online are mostly created by individuals with varying degrees of knowledge and skill. Some of the stuff is top notch quality while other stuff is total crap. Some of the crap goes unnoticed and therefore becomes spread all over, despite serious problems.
Know what you are collecting by looking for the following common problems with digital video.
PAL Speedup
When a 2 hour movie plays in 1 hour 55 minutes, and all of the actors voices are slightly higher in pitch, it tends to go unnoticed by the average collector. This problem is caused by PAL Speedup. It is an increase of 4.2% in pitch and speed that results from the conversion of film (or NTSC television) to the European PAL format. The 25fps PAL version of the movie ends sooner than it should because it played too fast. Once you become aware of it, you will never be able to ignore it. Videos with PAL Speedup should be marked as bad and not kept in your collection. Avoid video files of American films that have been converted to PAL (25fps.)
- See Section: PAL Speedup
Missing Forced Subtitles
It might be a Sci-Fi movie with aliens speaking in Klingon or a thriller with a few scenes of people speaking a foreign language, either way, most of us need English subtitles during these scenes, because we don't speak the factitious Klingon language or know what the foreign terrorist is saying. However, we don't need distracting subtitles throughout the entire movie for the English characters. Those subtitles that appear only during the few non-English parts are called "Forced Subtitles" and many people neglect to include them when creating the digital movie file from the source. It requires some extra effort. There are examples where perhaps only five lines of forced subtitles are in the movie, but we still want them included in a quality digital video. The YIFY group has gotten bad about neglecting to include them. Avoid video without forced subtitles. Give them low ratings.
- See Section: Forced Subtitles
Incorrect Aspect Ratio
The actors appear short and fat, or strangely tall and thin, because the image is stretched either vertically or horizontally. Sometimes an incorrect aspect ratio is caused by a video mastered from a European source converted to the North American standard, and other times the person creating the video simply did not use the correct settings in the encoding software. Video players such as VideoLAN Player can override the incorrect aspect ratio thus making the video appear correct for that particular viewing. However, with some media devices the problem cannot be corrected. Aspect ratio can sometimes be corrected by modification of the video header, depending on the encoding used.
Cinema Aspect Ratios from the video source should be preserved. Since most modern Blu-ray movies are released in 2.39:1 aspect ratio, you get bars across the top and bottom of the screen when viewing on your home 16:9 LCD television. This is fine and preferred over stretching the image during encoding. Stream and container mismatches also result in aspect ratio problems. One common mismatch is a 2.37:1 stream using a 1.78:1 container.
Related to video with an incorrect aspect ratio are problems such as over-cropping and capture of the black area in letterbox source. These are also issues to be aware of.
Over Encoding
If you see a 2 hour video that is 4 GB in size or larger in H.264, it is over encoded. There is more bit information captured than what is necessary. Even if you have a 74" wide screen high definition television you are not going to be able to discern the quality difference in a properly encoded H.264 that is 1.2 GB in size compared to an over encoded 4.6 GB video. Furthermore, a 720p video is better than a 1080i. For a 2 hour movie at 720p in H.264 with a file size of just under 1GB, the quality is going to be superior to a store bought DVD. If you feel you need 1080 HDTV video make sure it is progressive scan (1080p) and not interlace (1080i) and look for one that is re-encoded using H.264 with a file size around 2GB for a 2 hour video. Anything more is just a waste of bandwidth and hard drive space. Even if hard drive space is cheap, why be inefficient? Also, for a LAN video server that streams to mobile devices, the 720p video files are much easier to digest.
The H.264 codec is great at creating highly compressed video with excellent quality. That is what the codec is for. You are not taking advantage of H.264 if you have a nearly uncompressed video. With older codecs such as XviD, quality loss is noticeable, yet not terrible, when trying to achieve file sizes at around 800mb for a 2 hour movie with a 720p source. No quality loss is noticeable by the human eye when doing the same using H.264. Even more interesting is the fact that the more you compress a video in H.264 the better the codec works, up to a point. Finally, quality cannot be added back. When someone creates a video file at 1080p but used a DVD source, they are creating unnecessary replicated pixels with no additional quality. The file is huge when it is unnecessary.
Look for properly compressed H.264 video with reasonable file sizes appropriate for the length of the video.
