Video file quality differences

[helaku]

So, I have two episodes (same content, different encoding) and I want to tell me your opinion which have better quality for video and audio.
I am only interested in the quality opinions from the specs not from viewing, listening.

The first video file:
Video
ID : 0
Format : xvid
Codec ID : xvid
Duration : 7mn 3s
Bit rate : 804 Kbps
Width : 640 pixels
Height : 480 pixels
Display aspect ratio : 4:3
Frame rate : 29.970 fps
Bits/(Pixel*Frame) : 0.087
Stream size : 40.6 MiB (85%)

Audio
ID : 1
Format : MPEG Audio
Format version : Version 1
Format profile : Layer 3
Mode : Joint stereo
Codec ID : 55
Codec ID/Hint : MP3
Duration : 7mn 2s
Source duration : 7mn 2s
Bit rate mode : Constant
Bit rate : 128 Kbps
Channel(s) : 2 channels
Sampling rate : 44.1 KHz
Compression mode : Lossy
Stream size : 6.45 MiB (14%)
Alignment : Aligned on interleaves
Interleave, duration : 26 ms (0.78 video frame)

The second video file:
Video
ID : 0
Format : MPEG-4 Visual
Format settings, BVOP : 1
Format settings, QPel : No
Format settings, GMC : No warppoints
Format settings, Matrix : Default (H.263)
Muxing mode : Packed bitstream
Codec ID : DX50
Codec ID/Hint : DivX 5
Duration : 7mn 3s
Bit rate : 898 Kbps
Width : 512 pixels
Height : 384 pixels
Display aspect ratio : 4:3
Frame rate : 29.970 fps
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Compression mode : Lossy
Bits/(Pixel*Frame) : 0.152
Stream size : 45.3 MiB (87%)
Writing library : DivX 5.1.1 (Maupiti) (UTC 2003-11-19)

Audio
ID : 1
Format : MPEG Audio
Format version : Version 1
Format profile : Layer 3
Codec ID : 55
Codec ID/Hint : MP3
Duration : 7mn 3s
Bit rate mode : Constant
Bit rate : 128 Kbps
Channel(s) : 2 channels
Sampling rate : 44.1 KHz
Compression mode : Lossy
Stream size : 6.46 MiB (12%)
Alignment : Split accross interleaves
Interleave, duration : 33 ms (1.00 video frame)
Interleave, preload duration : 500 ms

Thanks!

[smrpix]

Quality can't be judged from numbers, only watching and listening. Especially when comparing apples to oranges as you are here.

[jman98]

I agree with smrpix, but assuming it's the same source, I'd expect the 2nd one to be better since it has a 10% higher video bit rate at a lower resolution.

[helaku]

I was only interested about the quality from the specs not from the watching, listening.
jman98, how DivX 5-898bitrate-512x384 have better quality than xvid-800bitrate-640x480?
From this comparison DivX 5 have 98kbps more than Xvid but have low resolution than Xvid.
How this thing is working? I don't understand.
Thanks!

[jagabo]

It depends on the nature of the video. Download the videos in this post:

https://forum.videohelp.com/threads/295672-A-problem-for-video-experts?p=1811057&viewfu...=1#post1811057

Look at their stats and decide which you think is best. Then watch them.

[helaku]

I understand that jagabo.
But how is the equation for high bit rate low resolution vs low bit rate high resolution? This I don't understand.
Thanks!

[jagabo]

First of all, resolution is part of the "quality" of the video. Otherwise we'd all reduce the frame size of our videos to 1x1 pixel and encode them losslessly and have "perfect" quality. So the first video, at 640x480, has that advantage.

All else being equal, the more bitrate you use on a video the better the the quality. But at some point using more bitrate delivers very little additional quality -- to the point where you can't seen any difference anymore. Where that point is varies from video to video. Bigger frame sizes and higher frame rates require more bitrate. Bright, high contrast content requires more bitrate. More detail requires more bitrate. Motion, action, noise, fire, splashing water, flickering lights, fog, smoke, etc. all require more bitrate. Basically, anything that causes the picture to change from frame to frame requires more bitrate. Your second video has the higher bitrate advantage.

The skill of the person performing the conversion and the encoder settings have an effect on the quality. We can't know about those.

Your first video has a larger frame size but a lower bitrate. If the content needed a high bitrate that video will have more macroblock artifacts. But if the content didn't need a high bitrate it may look just fine. Given the length it might be animated -- which usually has lower bitrate requirements than non-animated material. In which case 800 kbps might be sufficient.

But in the end there's no way of knowing which is better until you've seen them both.

[helaku]

Wow, great answer jagabo. BIG thanks!
I've compared them side by side and I find that the quality is the same which I think is strange from my point of view (maybe I don't have a good eye to compare them).

[jagabo]

Look at some small text. The first video may be a little more legible because of the larger frame size. Use a screen magnifier to zoom in on the videos. Look for blocky artifacts and loss of small detail. Especially when there's lots of motion.

[helaku]

From a closer and more accurate inspection I found that video two have more blocky artifacts than the first video.
So the first one with high resolution and low bitrate have greater quality than the second one with low resolution and high bitrate.
Thank you very much jagabo for your help.