Timing of produced output

jerrys

Senior Contributor Location: New Britain, CT, USA (between New York and Boston) Joined: Feb 10, 2010 21:36 Messages: 1038 Offline

Solved by

Jul 10, 2012 20:59

I think I'm losing my mind (again).

I am trying to compare the quality of a file produced with the DVD-HD profile vs. one that was produced at approximately the bit rate PD calculated for "Smart Fit."

After producing the two files, I tried to compare them side by side as best I could. I was amazed and dismayed to find that the two videos were offset by around a minute by the time I got 15 minutes in.

In other words, what I saw at 15:00 in video #1 was not even close to what I saw in video #2 at 15:00. This is true even when I'm using the same player for each.

When I brought both files into PD and put them on the timeline, they did line up.

What the heck is going on here? How can this be? How can a player gain or lose time like a cheap watch?

These videos are over two hours long, so it will take me some work to figure out where the misalignment is happening. I'll do more poking around tomorrow, but I'd appreciate your thoughts.

This message was edited 1 time. Last update was at Jul 10. 2012 20:59

Jerry Schwartz

Dafydd B

Senior Contributor Joined: Aug 26, 2006 08:20 Messages: 11973 Offline

Jul 11, 2012 04:03

Hi Jerry,
Please have a look at the frame rate of each. My guess is the Smart Fit will have a variable frame rate whereas the other will be more constant. Check the number of frames against each. Placement into PD is time/length based and is less reliant on frame rate base. I'm guessing here so any additional info would be useful.

One way for a file to be reduced in "size" is to remove frames while retaining the frame size. for example a 10fps video will be smaller than a 30 fps because the frames are less. It does of course depend upon the bitrate per frame.

The interpretation of the file by your players maybe related to the frame rate... still guessing.

MediaInfo should give you the data.

Dafydd

jerrys

Senior Contributor Location: New Britain, CT, USA (between New York and Boston) Joined: Feb 10, 2010 21:36 Messages: 1038 Offline

Jul 11, 2012 17:42

According to MediaInfo, there are very few differences between the two:

SmartFit:

General
Complete name : C:\Users\Jerry Schwartz\Videos\CaseyWedding\ReceptionFit\Fit.mpg
Format : MPEG-PS
File size : 3.90 GiB
Duration : 1h 48mn
Overall bit rate : 5 123 Kbps

Video
ID : 224 (0xE0)
Format : MPEG Video
Format version : Version 2
Format profile : Main@Main
Format settings, BVOP : Yes
Format settings, Matrix : Default
Format settings, GOP : M=3, N=15
Duration : 1h 48mn
Bit rate mode : Variable
Bit rate : 4 765 Kbps
Nominal bit rate : 6 000 Kbps
Width : 720 pixels
Height : 480 pixels
Display aspect ratio : 4:3
Frame rate : 29.970 fps
Standard : NTSC
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Interlaced
Scan order : Top Field First
Compression mode : Lossy
Bits/(Pixel*Frame) : 0.460
Stream size : 3.63 GiB (93%)

Audio
ID : 189 (0xBD)-128 (0x80)
Format : AC-3
Format/Info : Audio Coding 3
Mode extension : CM (complete main)
Muxing mode : DVD-Video
Duration : 1h 48mn
Bit rate mode : Constant
Bit rate : 256 Kbps
Channel(s) : 2 channels
Channel positions : Front: L R
Sampling rate : 48.0 KHz
Bit depth : 16 bits
Compression mode : Lossy
Delay relative to video : -53ms
Stream size : 199 MiB (5%)

[b]"Normal"

General
Complete name : C:\Users\Jerry Schwartz\Videos\CaseyWedding\Reception\Full.mpg
Format : MPEG-PS
File size : 6.31 GiB
Duration : 1h 48mn
Overall bit rate : 8 295 Kbps

Video
ID : 224 (0xE0)
Format : MPEG Video
Format version : Version 2
Format profile : Main@Main
Format settings, BVOP : Yes
Format settings, Matrix : Default
Format settings, GOP : M=3, N=15
Duration : 1h 48mn
Bit rate mode : Variable
Bit rate : 7 874 Kbps
Nominal bit rate : 8 300 Kbps
Width : 720 pixels
Height : 480 pixels
Display aspect ratio : 4:3
Frame rate : 29.970 fps
Standard : NTSC
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Interlaced
Scan order : Top Field First
Compression mode : Lossy
Bits/(Pixel*Frame) : 0.760
Stream size : 5.99 GiB (95%)

Audio
ID : 189 (0xBD)-128 (0x80)
Format : AC-3
Format/Info : Audio Coding 3
Mode extension : CM (complete main)
Muxing mode : DVD-Video
Duration : 1h 48mn
Bit rate mode : Constant
Bit rate : 256 Kbps
Channel(s) : 2 channels
Channel positions : Front: L R
Sampling rate : 48.0 KHz
Bit depth : 16 bits
Compression mode : Lossy
Delay relative to video : -53ms
Stream size : 199 MiB (3%)

Jerry Schwartz