File size issue after converting videos with XviD4PSP 5~

[Needles]

I was hardsubbing videos and I noticed something strange with the file size of the videos.
I hadsubbed 10 (mkv) videos into AVI Hardware and they all have the same output file size which is 287 mb. Most of them have a lesser amount of file size compared to the original videos but why are they all 287 mb?

Weird thing is that I also hardsubbed the videos into the same mkv format but they all have different AND lesser file size.

Hardsubbing a single video into mkv format takes up to 4-6 hours but still retains its 1280X720 resolution. When I hardsub a single video into AVI Hardware, it takes a little over 30 minutes but with its resolution reduced to 640X360. That being said, why is the file size of the mkv output videos lesser than the output file size of the videos that have been converted into AVI Hardware?

I'll list it and give 5 examples of the exact file sizes for each format so that it'll be more clarified~

**FILE SIZE OF THE ORIGINAL VIDEOS (SOFTSUBS + MKV FORMAT + 1280X720 RESOLUTION)**

~Episode 1: 352 MB
~Episode 2: 351 MB
~Episode 3: 240 MB
~Episode 4: 285 MB
~Episode 5: 459 MB

Total Size: 1.64 GB

-------------------------------

**FILE SIZE OF THE FIRST CONVERTED OUTPUT (HARDSUBBED + MKV FORMAT + 1280X720 RESOLUTION)**
{Converting time for a single video: 4-6 hours}

~Episode 1: 209 MB
~Episode 2: 219 MB
~Episode 3: 187 MB
~Episode 4: 206 MB
~Episode 5: 223 MB

Total Size: 1.02 GB

**FILE SIZE OF THE SECOND CONVERTED OUTPUT (HARDSUBBED + AVI [HARDWARE] FORMAT + 640x360 RESOLUTION)**
{Converting time for a single video: A little over 30 minutes}

~Episodes 1-5: 287 MB

Total Size: 1.40 GB

[jagabo]

With the AVI encodes you used bitrate based encoding where you set the bitrate (and hence file size since file size = bitrate * running time). So you get the file size you want but you don't know exactly what the quality will be. Since all your sources have the same running time they all have the same final file size.

With the MKV encodes you used a quality based encoding where you specify the quality you want and the encoder uses whatever bitrate is required to deliver that quality. Hence you know what the quality of the resulting video will be but you don't know the exact size.

I'm guessing the the AVI encodes used Xvid and the MKV encodes used x264. Xvid is faster but doesn't compress as well. It's possible to use faster settings with x264, at a slight cost in quality and file size.

[Baldrick]

Bitrate * running time = file size.

So what bitrate settings are you using? Click on the configure button next to the video codec to adjust it.

[Needles]

With the AVI encodes you used bitrate based encoding where you set the bitrate (and hence file size since file size = bitrate * running time). So you get the file size you want but you don't know exactly what the quality will be. Since all your sources have the same running time they all have the same final file size.

With the MKV encodes you used a quality based encoding where you specify the quality you want and the encoder uses whatever bitrate is required to deliver that quality. Hence you know what the quality of the resulting video will be but you don't know the exact size.

I'm guessing the the AVI encodes used Xvid and the MKV encodes used x264. Xvid is faster but doesn't compress as well. It's possible to use faster settings with x264, at a slight cost in quality and file size.

That makes sense. Now that you mention it, the files do have the same running time. Since it's based on bit rate and running time, so the file size of a video encoded using AVI Hardware is pretty much fixed before conversion?

[jagabo]

Since it's based on bit rate and running time, so the file size of a video encoded using AVI Hardware is pretty much fixed before conversion?

As Baldrick pointed out:

file size = bitrate * running time

Plus a little overhead for the container.