Variable Frame Rate MP4 - Revision history

Ballofsnow: /* Understanding the VFR process */

2007-12-31T08:00:47Z

‎Understanding the VFR process

Ballofsnow at 18:05, 27 December 2007

2007-12-27T18:05:48Z

Ballofsnow: /* Timecodes, finding the frame ranges */

2007-12-27T17:59:36Z

‎Timecodes, finding the frame ranges

Ballofsnow: /* Calculating the correct video bitrates */

2007-12-27T17:36:15Z

‎Calculating the correct video bitrates

Ballofsnow at 17:35, 27 December 2007

2007-12-27T17:35:22Z

Ballofsnow: /* Understanding the VFR process */

2007-12-27T04:08:30Z

‎Understanding the VFR process

Ballofsnow: /* Avisynth script */

2007-12-27T04:04:37Z

‎Avisynth script

Ballofsnow at 04:03, 27 December 2007

2007-12-27T04:03:39Z

Ballofsnow at 02:34, 27 December 2007

2007-12-27T02:34:19Z

Ballofsnow: /* Finding the frame ranges */

2007-12-27T02:23:04Z

‎Finding the frame ranges

@@ Line 14: / Line 14: @@
-. Using Avisynth, we can change the framerates of each video so that they match, and can thus be joined. Of course this will make parts of the video play faster or slower than it should. As you can see, changing the framerate from 60 to 30 has doubled the length of Video2.
+. Using AviSynth, we can change the framerates of each video so that they match, and can thus be joined. Of course this will make parts of the video play faster or slower than it should. As you can see, changing the framerate from 60 to 30 has doubled the length of Video2.
 [[Image:vfr2.png]]
@@ Line 24: / Line 24: @@
-. Now to get the video to play like normal again, we tell tc2mp4 which parts should be set to the original framerate. The result is a variable framerate video.
+. To get the video to play like normal again, we tell tc2mp4 which parts should be set to the original framerate. The result is a variable framerate video.
 [[Image:vfr4.png]]

← Older revision		Revision as of 18:05, 27 December 2007
Line 24:		Line 24:


−	4. Now to get the video to play like normal again, we tell tc2mp4 which parts should be set to the ~~orignal~~ framerate. The result is a variable framerate video.	+	4. Now to get the video to play like normal again, we tell tc2mp4 which parts should be set to the original framerate. The result is a variable framerate video.

	[[Image:vfr4.png]]		[[Image:vfr4.png]]

@@ Line 97: / Line 97: @@
 ==Timecodes, finding the frame ranges==
-To calculate the frame ranges from the AviSynth script above, first find out how many there are in each set.
+How difficult it is to find the frame ranges depends on the complexity of your AviSynth script. There's no easy way to do this, unless you're a scripting god, but you're already experienced enough that you should be able to figure it out.
-From the script above, if the 30 fps video had 1000 frames, and the 60 fps video had 2500 frames, then your timecode.txt file would be:
+An example: if a 29.97 fps video has 1000 frames, and a 59.94 fps video has 2500 frames, timecode.txt file will be:
 <pre><nowiki>
 # timecode format v1
-Assume 30
+Assume 29.97
-,999,30
+,999,29.97
-,3499,60
+,3499,59.94
 </nowiki></pre>
 <br>

@@ Line 91: / Line 91: @@
 In the final stages when the temporary video gets stretched/shrunk back to the real length, the average bitrate will be the correct 2048/5000.
-Now that you know the correct bitate, go ahead and encode the temporary video.
+Now that you know the correct bitrate, go ahead and encode the temporary video.
 <br>
 ==Timecodes, finding the frame ranges==

@@ Line 19: / Line 19: @@
-. Once joined, a temporary video is encoded with H.264 in the MP4 container.
+. Once joined, a temporary video is encoded with H.264.
 [[Image:vfr3.png]]
@@ Line 84: / Line 84: @@
 Temporary length = 5:11.333 = 311.333 seconds
-Ratio = 208.67 / 311.333 = 0.669
+Ratio = 208.167 / 311.333 = 0.669
 HQ 2048 * 0.669 = 1369 kbp/s<br>

← Older revision		Revision as of 04:08, 27 December 2007
Line 19:		Line 19:


−	3. Once joined, a temporary video is encoded with H.264 ~~/ AAC~~ in the MP4 container.	+	3. Once joined, a temporary video is encoded with H.264 in the MP4 container.

	[[Image:vfr3.png]]		[[Image:vfr3.png]]

@@ Line 46: / Line 46: @@
 vid2=vid2.changefps(vid1)
-AlignedSplice(a,b)
+AlignedSplice(vid1,vid2)
 ConvertToYV12()
 </nowiki></pre>
@@ Line 62: / Line 62: @@
 vid2=vid2.assumefps(vid1)
-AlignedSplice(a,b)
+AlignedSplice(vid1,vid2)
 ConvertToYV12()
 </nowiki></pre>

@@ Line 38: / Line 38: @@
 ==Avisynth script==
-As you saw in the pictures above, changing the framerate can change the video duration. Doing so also changes the duration of the audio which affects the pitch; not a good thing. So, the first goal is to create an audio file that sounds normal. Here's a simple AviSynth script:
+The first step is to extract the audio stream before we do any kind of video stretching. Here's a simple AviSynth script, modify it to your liking.
 <pre><nowiki>
@@ Line 50: / Line 50: @@
 </nowiki></pre>
-Modify it to your liking and encode the audio only. Once that's done it's time to prepare the real avisynth script. Simply change <b>changefps</b> to <b>assumefps</b> and encode the video.
+* Load the script into VirtualDub(Mod), go to File -> Information and write down the video length. For the sake of this guide, the length of the above script is 3:28.167.
 <pre><nowiki>
@@ Line 61: / Line 65: @@
 ConvertToYV12()
 </nowiki></pre>
 <br>
-==Finding the frame ranges==
+==Calculating the correct video bitrates==
 To calculate the frame ranges from the AviSynth script above, first find out how many there are in each set.

@@ Line 4: / Line 4: @@
 What is variable frame rate? You can probably guess that a constant frame rate is where the frame rate of a video stays the same throughout its whole length. In VFR you'll have sections that have a different framerate. VFR is useful when the game you've recorded has multiple in-game framerates. For example, God of War for the PS2 outputs gameplay at full framerate while its cinematics are half framerate.
 <br>
@@ Line 83: / Line 81: @@
 ==Setting the VFR==
-Your CFR encoding should be done now. Open a command line and use the following:
+Your encoding should be done now. Open a command line and use the following:
 <pre><nowiki>
@@ Line 89: / Line 87: @@
 </nowiki></pre>
-tc2mp4 gets rid of any audio in your files, so keep reading..
+tc2mp4 gets rid of any audio in your files so mux the one you made at the beginning of the guide.
 <br>

@@ Line 70: / Line 70: @@
 To calculate the frame ranges from the AviSynth script above, first find out how many there are in each set.
-From Example 1, if the 30 fps video had 23490 frames, and the 60 fps video had 25211 frames, then your timecode.txt file would be:
+From the script above, if the 30 fps video had 1000 frames, and the 60 fps video had 2500 frames, then your timecode.txt file would be:
 <pre><nowiki>
 # timecode format v1
 Assume 30
-,23489,30
+,999,30
-,48700,60
+,3499,60
-</nowiki></pre>
-−
-<font color="green"><b>Tip:</b> Write down the left hand side first by incrementing from the set above, then the end frame is just the one before.</font>
-−
-−
-From Example 2, since MvBob is a bobbing deinterlacer, it doubles the amount of frames. Don't forget that the first number in the trim command is inclusive. So the sets are 3442,2360,14800,975,2060,3195,1040, that's 27872 frames in total.
-−
-timecode.txt:
-<pre><nowiki>
-# timecode format v1
-Assume 29.970030
-,3441,59.940060
-,5801,29.970030
-,20601,59.940060
-,21576,29.970030
-,23636,59.940060
-,26831,29.970030
-,27871,59.940060
-</nowiki></pre>
-−
-Here is a batch file that should help generate the timecode file. It is intended for scripts that use mvbob and telecide, and the code must be similar to that of example 2. You can run the batch file from the command line and also by dragging an AviSynth script onto it.
-−
-<b>calcframeranges.bat</b>
-<pre><nowiki>
-@echo off
-REM Script written by Philip Cornell. Verion 1.1
-−
-REM If your video starts off with a statid, set the inc to however many frames it is.
-REM Once timecode.txt is generated, just change the first number back to 0.
-set inc=0
-−
-REM ##### SET THE FRAMERATES! #####
-set mrate=59.940060
-set trate=29.970030
-REM ##### SET THE PATH WHERE TIMECODE.TXT WILL BE SAVED ####
-set mypath=C:\change this and keep the slash at the end\
-−
-echo # timecode format v1 > "%mypath%\timecode.txt"
-echo Assume %trate% >> "%mypath%\timecode.txt"
-−
-FOR /F "tokens=2,3,4 delims=(,)" %%A IN ('find "last.Trim(" %1') do call :calc %%A %%B %%C
-echo timecode.txt successfully generated in %mypath%
-pause
-GOTO :EOF
-−
-:calc
-if /I %3==.mvbob set /A num=(%2 - %1 + 1) *2 & set rate=%mrate%
-if /I %3==.telecide set /A num=(%2 - %1 + 1) & set rate=%trate%
-set start=%inc%
-set /A inc=%inc% + %num%
-set /A end=%inc% - 1
-echo %start%,%end%,%rate% >> "%mypath%\timecode.txt"
-GOTO :EOF
 </nowiki></pre>