avidemux questions

[helms]

I have been experimenting with encoding 1080i PAL video and have some questions.

For some reason when you use the resize filter in avidemux to downscale it says 1920*1088 to whatever you want to scale to instead of 1920*1080 to what you want to scale to. Does avidemux add pixels to the video when it is opened to keep everything divisible by 16?

Which aspect ratio should I use 16:9 or 30:17 for the scaled resolution to keep everything proportional to the original?

Another question, when using both the crop filter and the resize filter with the crop filter first. Do you need to make sure the horizontal cropping from both sides is an even number and the vertical cropping from top and bottom are divisible by 4? Even if you are going to resize it after the cropping.

Should a deinterlacing filter be used when resizing if you want to keep the interlacing? Or is it not possible to keep the interlacing when resizing the video.

Yet another question, when I used mkvtoolnix to make the x264 avi I created with avidemux to use the mkv container it only decreased the size by 1 megabyte, is this the typical saving of mkv compared to avi, I got the impression from reading some articles that avi was very inefficient in regards to some of the functions of the x264 codec so I thought the saving would be more dramatic.

[LoRd_MuldeR]

Does avidemux add pixels to the video when it is opened to keep everything divisible by 16?

No, but the video has to be divisble by 16 to be encoded, as the compression is based on 16x16 blocks.

Which aspect ratio should I use 16:9 or 30:17 for the scaled resolution to keep everything proportional to the original?

Exactly the same, as the original has ?!?!?

Another question, when using both the crop filter and the resize filter with the crop filter first. Do you need to make sure the horizontal cropping from both sides is an even number and the vertical cropping from top and bottom are divisible by 4? Even if you are going to resize it after the cropping.

If you are going to resize afterwards anyway, you don't need to care about anything at the cropping stage. Only make sure, you resize to a mod16 resolution later.

Should a deinterlacing filter be used when resizing if you want to keep the interlacing? Or is it not possible to keep the interlacing when resizing the video.

If you want to resize interlaced video, you must ALWAYS deinterlace BEFORE resizing. Otherwise you end up with totally messed-up video!!! Of course deinterlacing is only an option, if you want to convert from interlaced to progressive. If you want to keep it interlaced, better avoid resizing at all! If you really cannot avoid it, the only way to resize interlaced video is: Deinterlace -> Resize -> Re-Interlace. A Filter-Chain for that in Avidemux would be: Separate Fields -> MPlayer Resize -> Merge Fields. Note that you need to set the resize filter to half the final vertical resolution when using this method (horizontal resolution is set normal)

Yet another question, when I used mkvtoolnix to make the x264 avi I created with avidemux to use the mkv container it only decreased the size by 1 megabyte, is this the typical saving of mkv compared to avi, I got the impression from reading some articles that avi was very inefficient in regards to some of the functions of the x264 codec so I thought the saving would be more dramatic.

There's much flame against AVI flying around in the net :rolleyes:

[foxyshadis]

Yet another question, when I used mkvtoolnix to make the x264 avi I created with avidemux to use the mkv container it only decreased the size by 1 megabyte, is this the typical saving of mkv compared to avi, I got the impression from reading some articles that avi was very inefficient in regards to some of the functions of the x264 codec so I thought the saving would be more dramatic.

AVI doesn't have any real issues with AVC, if you don't use b-frames or don't ever intend to edit it. (Don't ask us for help when editing goes badly, you probably won't get much.) It's the audio that causes real size issues. Alex Noe put together a comprehensive overhead table (http://www.alexander-noe.com/video/amg/en_overhead_comparison.html) for different formats.

Unfortunately, even with the containers that can store AVC correctly, avidemux is not yet able to decode frames in the right sequence, so it's a bit of a guessing game trying to edit that way. Commercial mp4 editors are the only sane option.

[helms]

I'm still a bit confused with the resolution of the video. 1080i is often used to refer to video with an aspect ration of 16:9, horizontal res of 1920 and vertical res of 1080. I'm not really sure where to look in the mplayer output but when I browsed through it I only saw 1920*1080.

However the resize thing in avidemux says 1920*1088 (ratio 30:17). Does that mean that even though mplayer reports 1920*1080 the actual video is 1920*1088.

Well I have already tried resizing the video with out deinterlacing first and the result didn't have any problems so I guess contrary to my belief that the video was interlaced I guess it's not.

[LoRd_MuldeR]

Unfortunately, even with the containers that can store AVC correctly, avidemux is not yet able to decode frames in the right sequence, so it's a bit of a guessing game trying to edit that way. Commercial mp4 editors are the only sane option.

ffmpegsource() can do it correctly, at least with my H.264 AVI's created in Avidemux :)
I really hope it can be implemented in Avidemux the same way as ffmpegsiurce() does one day....

[LoRd_MuldeR]

Well I have already tried resizing the video with out deinterlacing first and the result didn't have any problems so I guess contrary to my belief that the video was interlaced I guess it's not.

Interlaced video can only be detected by your own eyes! Make sure you inspect the video in a Player/Editor that doesn't deinterlace or resize the video! Avidemux is one tool that can be used for this purpose. Then carefully scan the video for "Combing" artifacts. Especially look at moving objects and check different scenes. In case the video is interlaced, you will see something like this:

http://100fps.com/distortion2.jpg
http://100fps.com/scene1_2.jpg
http://100fps.com/1a2.jpg


After resizing an interlaced video without proper deinterlacing, you end up with something like that, which is impossible to repair:

http://100fps.com/distortion1.jpg

[helms]

thanks for the help