MPEG Streamclip MPEG-TS to MPEG4/H264 (file size & aspect ratio query)

[Heathy65]

I have been using MPEG Streamclip to convert videos I have copied from my Topfield TF5810PVR to a format suitable for my Apple products.

The files from the Topfield are in MPEG2 TS format and I'm converting to MPEG4/H.264 format.

This is the Stream Information for an example source file as show by MPEG Streamclip:

Type: MPEG transport stream
Duration: 0:05:21
Data Size: 93.68 MB
Bit Rate: 2.45 Mbps
Video Tracks: 101 MPEG-2, 544 × 576, 16:9, 25 fps, 15.00 Mbps, upper field first
Audio Tracks: 102 MP2 stereo (joint), 48 kHz, 128 kbps


When I convert using MPEG Streamclip having selected "Export to MPEG-4" and used "Reset All", leaving all setting as default/unchanged (so using "1024 x 576 (16:9)", I get the following output:

Duration: 0:05:20
Data Size: 149.98 MB
Bit Rate: 3.93 Mbps
Video Tracks: H.264, 1024 × 576, 25 fps, 3.67 Mbps
Audio Tracks: MPEG-4 Audio stereo, 48 kHz, 256 kbps

The quality of this output is good but the file size has increased by about 50%.

I accept that there is a relationship between quality and file size, but you can't get something from nothing! Although I also appreciate that the efficiencies of the different video/audio codec may be coming into play here?

Also another thing that I don't understand is that the original files have a reported 544 x 576 resolution. I don't see how this can be right, since the pictures are in 16:9 format (and 544 x 576 means they are taller than they are wide!).


So I tried an export using the "544 x 576 (unscaled)" settings and got this output:

Duration: 0:05:20
Data Size: 101.86 MB
Bit Rate: 2.67 Mbps
Video Tracks: H.264, 544 × 576, 25 fps, 2.41 Mbps
Audio Tracks: MPEG-4 Audio stereo, 48 kHz, 256 kbps

So the file size is 101MB (so pretty close to the original and about 50% smaller than the 1024 x 576 one).

The problem with this export is the output files have the wrong aspect ratio. I have experimented with the Zoom and X/Y options too but every combination I try produces output with the wrong aspect ratio.

So it looks like I need to stick with the "1024 x 576 (16:9)" option, which I understand since that's the format I want but I don't understand why the input files are being reported as "544 x 576" and also why my output files are so large in comparison to the input files.

I can provide an example file if necessary/helpful.

[Baldrick]

The video can be in 544x576 resolution(or any size) but with a 16:9 display aspect ratio and it will look fine in all players that reads the display aspect ratio.

You can adjust the display aspect ratio in the new mp4 with mp4box (command line tool for windows/mac/linux) like

mp4box -par 1=33:17 video.mp4

Calculate the par value with http://tools.rodrigopolo.com/mp4box_aspect_fix/


Or if you are making it 1024x576 then lower the bitrate to get smaller output size.

[Heathy65]

Excellent, thanks for the information.

I tried mp4box after my conversions with MPEG Streamclip (using 544x576) and that worked fine

However, if I stick with just using MPEG Streamclip (i.e. no post processing with MP4Box) and leave the settings at 1024x576 then clearly that's fine too but the file sizes are significantly bigger.

I want the output quality to be as good as reasonably possible but am I correct in assuming that there's no benefit of going above 544x576 since that's the restriction of the input files?

[Baldrick]

Some media players might ignore the display aspect ratio in the mp4 and it will look stretched. Then must you resize to 1024x576 (16:9 pixel aspect ratio).

But to get smaller size adjust the bitrate, choose Limit Data Rate. Use same as the source and it will be same size.

[Heathy65]

Ah I see, that seems a better option.

I've just tried what you suggest, i.e. limiting the data rate and using the 1024x576 (16:9) option without any MP4Box post-processing and I get what I want.... a good quality and good file size

Thanks very much for your help, it's appreciated.

[Chamelet]

Sorry to intrude and talk about something not exactly related to the topic, but derived from it.

I have been witnessing an issue with MPEG Streamclip scaling. It seems to crop the image on the side a little bit. Any of you noticed this? I opened a topic about it, if you can help me...

https://forum.videohelp.com/threads/345063-MPEG-Streamclip-aspect-conversion-actually-c...s-the-image%21