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| Djard |
| Posted: Nov 26 2013, 05:45 AM |
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Member
Group: Members
Posts: 16
Member No.: 26022
Joined: 17-August 09
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I have a movie that suffers audio drift. The AV sync is OK at the beginning but by the end of the movie, the audio trails the video by about 750 ms. Yet "File Information" states that the video length is 1:44:37.65 and the audio is 1:42:32.83.
When I set "Audio skew correction" to delay the audio track by "-750 ms," the end of the movie is in perfect sync, but then the audio plays too early at the start.
So I tried slowing down the framerate incrementally but could not get it right. I gave up on that option after an hour.
Then I used the "Change so video and audio duration match" feature to make the A & V the same length. The asynchrony became much worse. Setting the "Audio skew correction" to delay -3100 got the start in sync but then the rest got so far off that the audio disappeared.
Can give me a little guidance? |
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| dloneranger |
| Posted: Nov 26 2013, 06:11 AM |
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Moderator
Group: Moderators
Posts: 2366
Member No.: 22158
Joined: 26-September 07
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Yeah, audio skew just moves the audio forwards or backward as a whole
You need to slow down the video or shrink the audio
Try multiplying your fps by 1.0000047788583307447850708465748 and changing the frame rate to that
Or you can stretch the audio instead using the advanced audio filters
- add input, time stretch, output
- set time stretch value to 0.99999522116450663302366479336315
To get those numbers I used your figure for the video 1:44:37.65 and the .75 difference at the end
x= 1*60*60 + 44*60 +37 +.65 = duration in seconds for avi
y= duration in seconds for avi + .75
x/y = ratio of difference in length
[edit]
Don't trust my maths here, it was way too early in the morning
Use the answers from people below who seem to have actually been awake 
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MultiAdjust JoinWav WavNormalize FFMPeg Input Plugin v1827 UnSharpMask
Windows7/8 Codec Chooser
All FccHandlers Stuff inc. Installers for acm codecs AAC, AC3, LameMp3 |
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| malky |
| Posted: Nov 26 2013, 11:33 PM |
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Advanced Member
Group: Members
Posts: 290
Member No.: 22386
Joined: 6-November 07
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Help, I keep getting the wrong answer.
x=6277.65
y=6278.4
x/y=0.99988054281345565749235474006116
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| meowmeow |
| Posted: Nov 27 2013, 01:09 AM |
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Advanced Member
Group: Members
Posts: 98
Member No.: 37160
Joined: 21-September 13
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No, its
41851/41856=0.9998805(428134556574923547400611620795107033639143730886850152905198776758409785932721712538226299694189602446483180)
Sometimes I just mux into .mkv and players sync films correctly. Not sure why. |
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| dloneranger |
| Posted: Nov 27 2013, 05:35 AM |
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Moderator
Group: Moderators
Posts: 2366
Member No.: 22158
Joined: 26-September 07
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Am I being mocked?
It looks like I'm being mocked
I am, I'm being mocked!!!! 
Maths in the morning before I go to work is harder than it looks 
If you'll both submit your papers (with all the workings out!) I'll have them graded by friday
@malky
you'll lose half a point for the woefully small amount of digits
@meowmeow
wolfram alpha????
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| meowmeow |
| Posted: Nov 28 2013, 02:18 AM |
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Advanced Member
Group: Members
Posts: 98
Member No.: 37160
Joined: 21-September 13
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| QUOTE (dloneranger @ Nov 27 2013, 05:35 AM) | | wolfram alpha???? |
GNU Basic Calculator
| QUOTE | c:\BC\bin>bc meow.bc
bc 1.06
Copyright 1991-1994, 1997, 1998, 2000 Free Software Foundation, Inc.
This is free software with ABSOLUTELY NO WARRANTY.
For details type `warranty'.
scale=2
x= 1*60*60 + 44*60 +37 +.65
y=x+.75
scale=300
meow(x,y)
41851/41856=.9998805428134556574923547400611620795107033639143730886\
85015290519877675840978593272171253822629969418960244648318042813455\
65749235474006116207951070336391437308868501529051987767584097859327\
21712538226299694189602446483180428134556574923547400611620795107033\
639143730886850152905198776758409785932720
quit
c:\BC\bin> |
Contents of meow.bc
| CODE | # License: LGPLv2 Author: http://www.pixelbeat.org/scripts/bc
define gcd(x,y) {
if (y==0) return x
return gcd(y,x%y)
}
# License: SFBTL (steal fast before too late!) Author: meowmeow
define meow(e,w){
s=scale; e*=10^s; w*=10^s; scale=0; o=gcd(e,w); e/o; " / "; w/o; " = "; scale=s; return(e/w)
} |
This post has been edited by meowmeow on Nov 28 2013, 11:37 AM |
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| Djard |
| Posted: Nov 28 2013, 06:21 AM |
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Member
Group: Members
Posts: 16
Member No.: 26022
Joined: 17-August 09
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Wow, my calculator doesn't support that many digits. I can calculate Newtonian formulas in my head, like S=ut+1/2at squared, but you folks blow me away. I solved my problem as follows, but I will study the interesting option you kindly share of crunching the numbers.
Since slowing the video down to have the audio sync at the beginning AND the end was unlikely without a lot of time-consuming experimentation, my initial objective was to slow the video (by lowering the framerate) until the video latency at the start is the same as at the end of the movie. Remember that the movie was OK at the start but the audio drifted, lagging more and more behind the video. So if I synchronized the end by slowing down the video, the video would naturally lag behind the audio at the beginning. After two trials, a framerate of 23.972 fps had the video about 1/4 sec. behind the audio at both points, start and end.
Since the procedure is one of direct stream copy with no loss of video quality, I used the "Audio skew correction" feature to deleay the audio by 250 ms. I had already disabled "Sync to Audio" and "Audio/Video interleaving." I'm happy withy the result, not able to notice if there is any asynchrony at the start or end. Yay! |
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| meowmeow |
| Posted: Nov 28 2013, 06:44 AM |
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Advanced Member
Group: Members
Posts: 98
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| QUOTE (Djard @ Nov 28 2013, 06:21 AM) | | I had already disabled "Sync to Audio" and "Audio/Video interleaving." |
Sync to audio disables forced sync in VD preview mode only. For vbr mp3 probably.
Disabling interleaving actually disables AVI, writing audio in single block, making it unplayable for CD players I think. |
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| Djard |
| Posted: Nov 29 2013, 08:49 PM |
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Member
Group: Members
Posts: 16
Member No.: 26022
Joined: 17-August 09
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Thanks for the help.
I get the sense that something is loose in packaging: after synchronizing the AV in VD, I played the movie with MPC. The start and end remained synchronized. I then corrected the DAR with XMediaRecode, choosing the MP4 format. After converting the movie to DVD with ConvertX, I noticed the audio was delayed by 175 ms. Aaargh! So I converted again, using ConvertX's "Offset" feature, set at -175 ms to correct the new skew. I then burned to a rewritable disc and viewed the start and end on my TV. I was thrilled to find no discernable asynchrony. I just wonder how a movie can be so messed up: out of sync and aspect ratio way off.
Regarding the disabling of audio interleaving, Mediainfo reports the following, with 2 minutes disparity between the audio and video, yet the AV is synchronized. My guess is that someone trimmed the start:
General
Complete name : C:\DVD_TMP\My_Movie.mp4
Format : MPEG-4
Format profile : Base Media
Codec ID : isom
File size : 1.88 GiB
Duration : 1h 44mn
Overall bit rate : 2 568 Kbps
Encoded date : UTC 2013-11-28 01:53:44
Tagged date : UTC 2013-11-28 01:53:44
Writing application : Lavf55.19.100
Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : Main@L4.1
Format settings, CABAC : Yes
Format settings, ReFrames : 2 frames
Codec ID : avc1
Codec ID/Info : Advanced Video Coding
Duration : 1h 44mn
Bit rate : 2 437 Kbps
Nominal bit rate : 2 600 Kbps
Width : 720 pixels
Height : 404 pixels
Display aspect ratio : 16:9
Original display aspect ratio : 16:9
Frame rate mode : Constant
Frame rate : 23.976 fps
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.349
Stream size : 1.78 GiB (95%)
Writing library : x264 core 138 r2345
Encoding settings : cabac=1 / ref=2 / deblock=1:0:0 / analyse=0x1:0x131 / me=hex / subme=7 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=0 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=0 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=12 / lookahead_threads=2 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=3 / b_pyramid=0 / b_adapt=1 / b_bias=0 / direct=3 / weightb=1 / open_gop=0 / weightp=2 / keyint=230 / keyint_min=23 / scenecut=40 / intra_refresh=0 / rc_lookahead=40 / rc=abr / mbtree=1 / bitrate=2600 / ratetol=1.0 / qcomp=0.60 / qpmin=10 / qpmax=69 / qpstep=4 / vbv_maxrate=24000 / vbv_bufsize=24000 / nal_hrd=none / ip_ratio=1.40 / aq=1:1.00
Language : English
Encoded date : UTC 2013-11-28 01:53:44
Tagged date : UTC 2013-11-28 01:53:44
Audio
ID : 2
Format : AC-3
Format/Info : Audio Coding 3
Mode extension : CM (complete main)
Format settings, Endianness : Big
Codec ID : ac-3
Duration : 1h 42mn
Bit rate mode : Constant
Bit rate : 128 Kbps
Channel(s) : 6 channels
Channel positions : Front: L C R, Side: L R, LFE
Sampling rate : 48.0 KHz
Bit depth : 16 bits
Compression mode : Lossy
Stream size : 93.9 MiB (5%)
Language : English
Encoded date : UTC 2013-11-28 01:53:44
Tagged date : UTC 2013-11-28 01:53:44
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