Difference between revisions of "PAL Speedup"

Latest revision as of 13:18, 15 October 2023

PAL Speedup is a nasty side effect from the process of converting film into home video for European audiences. It results in distorted video. It is a widespread problem that is not sufficiently addressed in the Internet video community. In a nutshell, PAL Speedup is when a movie file plays slightly too fast, so it is shorter than it is supposed to be, and all the actor voices are slightly higher pitch than they should be. To some, it is not noticeable, while to others it is maddening. It is such a slight difference that it is right on the edge of human perception. Yet, if you notice it, then you don't like it.

• PAL video encoded frame rate 25fps from film or NTSC source
• People sound a little bit "chipmunk" (high pitch) and the film plays faster than intended
• Results from outdated source to digital processing and/or sloppy/ignorant job encoding

In Europe due to the oscillation of their electrical system frequency, they film movies at a different frame rate. Europe uses the PAL or SECAM video standards. For Europeans film destined for television are photographed at 25 frames per second. The PAL video standard broadcasts at 25 frames per second, so the transfer from film to video is clumsy. In this clumsy 2:2 pulldown, for every film frame, one video frame is captured. Theatrical features originally photographed at 24 frame/s are shown at 25 frame/s resulting in a 4% increase in playback speed. The increase causes a slightly noticeable increase in audio pitch by just over 0.679 semitones.

The process is also used when NTSC (North American) film and television is cover converted to be viewed by the European standard. If a work was originally created for European television, it will not be time shifted. Only works created for North American television converted to PAL, or film motion pictures converted to PAL.

PAL Speedup is causing the most problems in the world of digital video downloads. People download films from the Internet and are not aware of PAL Speedup. One film may be properly encoded from a proper NTSC source, while another may be shortened and higher pitch due to PAL Speedup. The overall impact is the propagation of this horrible high pitch, fast running PAL movies and video files spreading through the Internet by the uneducated and unaware public.

Exception: If a video is from original European production, such as a television program produced in the UK and is already PAL, the frame rate will be 25 fps source to 25 fps digital. In this event a digital video file of 25fps will not have any speedup, since the source was already 25 fps. When checking a video frame rate know that the mere fact it is 25 fps does not necessarily mean that it will be higher pitch and shorter duration. To verify PAL Speedup, you must know what the correct playtime is and compare that to the playtime of the file. Such exception cases represent the small minority of PAL video files you will encounter, most suffer from PAL speedup.

Video Playback Slightly Too Fast

The United States, like the rest of North America, use a video frame rate standard called NTSC. NTSC has a frame rate of 24 frames per second, of 24fps. PAL has a frame rate of 25fps. This relates to the electrical alternating current frequencies native to these regions. The U.S. is 60Hz while Europe is mostly 50Hz.

In NTSC television the rate is effectively slowed to 23.976 FPS (24×1000÷1001 to be exact), and when transferred to PAL or SECAM it is sped up to 25 FPS.

The difference in frame rate is causing problems in the digital video world. People in the NTSC world are finding videos that seem fine at first, but are subtly playing slightly too fast, and the pitch of all sound, including everyone's voice is slightly too high.

This issue has been called "PAL Speedup." Pal Speedup describes the increase of 4.2% in pitch and speed that results from the conversion of film (or NTSC-TV) to the european PAL format. This effect will cause the PAL version of a 2 hour movie will play in 1 hour 55 minutes.

• PAL Speedup
• PAL 4% Speedup

People in Europe are taking NTSC movies, and encoding them digitally, converting them to PAL, and in doing so, are causing the movies to be distorted in both time and pitch. When these distorted movies are shared via the Internet, such as on bittorrent, they end up back in the hands of people in North America. Some people don't realize they've collected and are sharing distorted media, and the bad movie files continue to propagate. What these European encoders should be doing is converting them digitally to the proper NTSC format, then using a media player that can play both PAL and NTSC. This would be much better than polluting the Internet and bittorrents with distorted "PAL Speedup" movies and video media.

Note: English-language films from PAL territories on DVD discs have the PAL speedup problem too. Ripping from a source like this results in a digital video file with PAL speedup. VHS tapes sold in PAL territories of American movies also are sold as-is with PAL speedup.

Bittorrents today are filled with a mix of properly encoded media, and distorted crap. It isn't uncommon to see highly rated downloads which are actually suffering from PAL Speedup. People doing encoding that lack the knowledge to do it correctly are the culprit. Movies suffering from PAL Speedup need to be rated low, and eradicated.

• PAL Speedup
• PAL's 4% Speedup

more background and references

Best described by a user on AfterDawn forums: "Anyone notice this problem? It seems to be with some xvid or divx videos I've downloaded. The speed difference is so slight that you really can't tell until you watch the original and hear that the theme song is in a lower key and the voices are lower."

source: AfterDawn > Forums > Video playback problems > video plays slightly too fast

Files playing at 25fps but were filmed at 24fps will cause this problem. For European PAL TVs the film is simply sped up the 4.16%. The sound is also sped up and is a half-step too high. People are not encoding the files properly, and the difference is just too slight to notice.

Judging by the running times, I would guess the source was probably 24fps film. The 25 fps AVI probably came from a PAL DVD where the film is sped up to 25 fps. The 25 fps AVI retained that frame rate and probably has smooth, though slightly fast playback (compared to the original film).

Film can be shot at either 24fps or 25fps for PAL. There are two ways to transfer the film to tape.

Telecine A: 25 FPS frame-for-frame from the negative or workprint. Either film that originated at 24 FPS or 25 FPS can be transferred this way. If the film was shot at 25 FPS, there is no modification in the playrate. If the film was shot at 24 FPS, it is being played 4.166% faster.

Telecine B: 24 FPS adding a field at the 12th and 24th film frame (24 FPS film is cine-expanded to 25 frames). Film shot at 24 FPS is played at that rate with an additional frame generated in the telecine process so one second of film still plays at that duration on the PAL tape.

A lot of bad video is being distributed by people who do not know how to properly encode. It goes unnoticed since the speed difference is so slight. However, it is bad quality video.

• Compensate for PAL Speedup in Digital Video - Guide with various methods to deal with PAL video that has speed-up as a result of telecine process.

Have you been annoyed by PAL-encoded movies playing a little faster than usual, where the music's tempo is wrong and everyone talks a little faster?

If you have VLC, here's how to fix it:

   Open VLC.
   Go to the 'VLC' menu and select 'Preferences…'
   In the radio buttons in the lower-left corner of the window, change 'Basic' to 'All'.
   Click on 'Input / Codecs' in the left-hand side list.
   In the right-hand side frame look for 'Playback speed' and change it to 0.96 (use a comma if your system uses that as the decimal separator).
   Click on 'Audio' in the left-hand side list.
   In the right-hand side frame disable 'Enable time stretching audio'.
   Click the 'Save' button on the lower-right corner of the window.
   Quit and relaunch VLC.

Here is a command line switch example using VLC:

"C:\Program Files\VideoLAN\vlc.exe" "c:\palvideo.wmv" --no-audio-time-stretch --rate=0.96

The NTSC standard is 29.97 fps, and PAL is 25 fps. And if this hint is talking about what I assume it is, not all PAL videos are affected, and it has nothing directly to do with VLC (although the workaround here should work, in principle). The problem is that theatrical movies are normally filmed at 24 fps, not 25 or 30. A process called 3:2 pulldown (too lengthy to go into the details here) converts such movies to the nearly 30 fps rate required on NTSC systems, and the playback speed ends up very close to the original. On PAL systems, the common approach is to simply speed up the movie from 24 to 25 fps, shortening the playback time. Sometimes the soundtrack is processed to prevent the sound from raising in pitch, but that varies with the movie.

AGKnot request: Now how bout those pesky PAL DVDs

Convering FILM to PAL without 4% speed-up (frame/field blending?)

24fps NTSC films are sped up to 25fps when converted to PAL. The audio is sped up with the video so there will be a change in pitch. The speed difference is 4% which results in the PAL disc having a shorter duration, but all frames are still there.

Reclock

"For reference, fixing this nonsense is easily accomplished on playback (on a PC anyway) by using ReClock."

(using reclock is an ugly patch, not a good solution)

The following is an excellent discussion on the topic:

• How to convert x264 HD 25fps to 23.976fps

Fast dirty method with VirtualDub:

1. File -> Open AVI File.
2. Video -> Frame Rate... in Frame Rate Conversion section enable Convert To FPS and set 23.976 or 25.
3. Video -> Compression... select compression codec and settings (Xvid, target quantizer 3?)
4. File -> Save as AVI.

The result will be a little jerky.

source: Forum Video Video Conversion Changing AVI from 29fps to 25fps

Doom9's Forum > Announcements and Chat > General Discussion > PAL and NTSC running times - what a spin-out!

Movies or television shows that were originally 24fps (as all movies, and most U.S. television shows are), but have been converted to 25fps for PAL playblack.

The conversion of 24fps source material to 25fps is pretty simple:

• speed up the playback rate by 1.0466%

This has the effect of turning a 2h 20m movie into a 2h 14m 24s movie. It also has the undesirable side-effect of increasing the pitch by a full note. This gives everyone speaking a chimpmunk quality.

source: http://superuser.com/questions/320127/converting-movie-from-25fps-pal-back-to-24fps-without-recompressing

PAL Speedup Example

See the "Talk" section: Talk:PAL_Speedup

"The evil of the PAL speedup, the process in which NTSC original are sped up by 4% to run at our speed without any side effects. Except when you notice it, you can't unnotice it."

See: http://cyberside.net.ee/ripping/PAL%20Speedup%20%20Examples.htm

Stop Spreading PAL Garbage!

When you come across a film or video that suffers from the PAL 4% Speedup, you should take all efforts to flag it as "bad" and delete and destroy all copies possible. The archiving of our video art and culture should not be distorted in time and pitch due to the ignorance of video pirates and uneducated encoders.

• Know what PAL Speedup is
• Know how to detect PAL Speedup
• Take action to prevent and destroy distorted PAL Speedup media

Video encoded in any format, with any degree of high definition is no good when suffering from PAL Speedup.

Discussion of reversing PAL speedup

I. You can use command line parameters to force a workable video player to compensate for PAL speedup, thus restoring the proper audio pitch and playtime duration.

VLC Player aka VideoLAN Player will easily accomplish this and has been able to for many versions to present. Example:

vlc -f videofilename.avi --no-audio-time-stretch --rate=0.96 --no-embedded-video --no-sub-autodetect-file vlc://quit 

If you install zenity on your linux system you can use the following shell script called [altplayer] which will give you a dialog and allow you to choose NTSC or PAL when launching VLC to play a video.

See Also: Compensate for PAL Speedup in Digital Video.

VLC can be made to correct for the speed and audio pitch problems introduced by crappy PAL video in multiple ways besides using command line parameters.

If you have VLC, here's how to fix it:

   Open VLC.
   Go to the 'VLC' menu and select 'Preferences…'
   In the radio buttons in the lower-left corner of the window, change 'Basic' to 'All'.
   Click on 'Input / Codecs' in the left-hand side list.
   In the right-hand side frame look for 'Playback speed' and change it to 0.96 (use a comma if your system uses that as the decimal separator).
   Click on 'Audio' in the left-hand side list.
   In the right-hand side frame disable 'Enable time stretching audio'.
   Click the 'Save' button on the lower-right corner of the window.
   Quit and relaunch VLC.

Here is a command line switch example using VLC:

"C:\Program Files\VideoLAN\vlc.exe" "c:\palvideo.wmv" --no-audio-time-stretch --rate=0.96

Question: Can a flag be set in the video file such as a tag in an mkv file to instruct a video player that it shall apply PAL speedup compensation?

Answer: Theoretically this is very possible. As to practical application it is unknown if any current video players or flag/tag standard exists to accomplish this. The digital video community has mostly tended to ignore this problem although something of the sort might exist by the time you read this.

II. You can re-encode or convert PAL speedup videos back to NTSC with the correct audio pitch and playtime.

There are different tools to accomplish this. There are also some side effects such as the introduction of slight jerkiness in video from things like duplicated frames depending on the process you use. The sample rate of the audio needs to be changed so the audio is stretched to the correct playtime. Then the video has to be stretched (which may involve the replication of frames) to match the audio runtime.

Stretching the audio so that the audio tract is at the correct pitch and total length in runtime involves the formula calculated by ((24000/1001) / 25) * 48000. Then the video can be stretched which involves extracting the video stream then a mux to put it back with the corrected audio stream. (1). Separate audio and video into 2 files. (2). process audio to correct pitch and runtime (3). process video to correct play length (4). mux correct audio and video into new file.

For the audio track the process is lossy. For the video track this depends on the software and method you use which may either introduce a slightly noticeable jerkiness in the video or some loss in quality.

From a video discussion forum a bash/shell script that uses ffmpeg:

ffmpeg -loglevel info -y -i "$file" -map 0 -c copy -c:a ac3 -filter:a aresample=resampler=soxr,asetrate=46033.92 -ar 48000 tmp.mkv
mkvmerge -o "$outfile" --default-duration 0:23.976fps tmp.mkv

In this person's example the change in video speed is lossless, only the metadata gets updated.

Here is another example:

ffmpeg -i input.mkv -filter_complex "[0:V:0]setpts=25/24*PTS[vout];[0:a:0]asetrate=46080,aresample=resampler=soxr:osr=48k[aout]" -map "[vout]" -map "[aout]" -r:v 24/1 -vsync vfr output.mkv

A new problem is introduced when you have subtitles. If the subtitle track has already been timestamped to match the PAL video, the subtitles will lose synchronization with the newly corrected video. This is especially troublesome with Forced Subtitles that are in their own track, like an srt embedded into an mkv file. If the track is forced subtitles you might find that editing the timestamps in the file by hand with a text editor your only remedy. This is less practical with a full line by line subtitle track. Additional software is required or a clever bash script involving regex.

III. You can adjust the audio pitch and ignore the faster playtime (not recommended).

The audio file is not stretched, but processed so that the pitch is decreased to match the original pitch of the sound. However, speech and audio will still be delivered faster than the original. Imagine the actor being perceived as delivering a line faster than the original and yet not sounding higher pitched, just seeming to talk faster. Human perception is not likely to notice the subtle time shift as long as the actor does not seem higher pitch in sound.