50p video just patched to play back as 25p - can it be done?

[larioso]

Hi
Thinking to do slow motion so no audio or anything.
Just telling player to play back - this is 25p, nothing else?

Some camcorders have slow mo option for 50p playback only as I discovered, no clue why.

Just patching like this would not implicate any quality I presume. You would just get I-frame(full frame) half as often if H264.
It's slow motion anyway.

What tools to use or does video editors have this non destructive patching?

Thanks.

[jagabo]

Many players have the ability to play at half speed. You can remux the video with the header marked for half the original frame rate. Some players may not respond to this. MkvToolnix also lets you update the bitstream timecodes which should work with every player.

[larioso]

Thanks for an insightful read, never thought about timecode implications for each frame. Will check out software you linked to.

What I am aiming for is to have ordinary photage and slow mo photage mixed in scenes in video editor - and render with as little loss as possible. And issue here is that one camcorder I look at have slow mo only at 50p - and rest of film will be 25p.
Many editors also have a special marking whether this clip will be converted in some way or not - and best is if untouched all the way.
So I'm thinking end product on YT uploaded as MP4 and just working for anybody with full quality sharing as video clips.

[DeJay]

Some NLEs allow the fps of a clip to be changed while on the timeline via clip properties, which for a 50p clip can double its length and therefore half the playback speed.

[larioso]

Thank you.
I'll give it a shot and do a short video at 50p and try and see what happends - if the options are there.

[manono]

I'll give it a shot and do a short video at 50p and try and see what happends - if the options are there.

Slowing it to half speed in an NLE requires a full reencode. You specifically asked to retain full quality.

You'll be better served trying jagabo's suggestions followed by seeing if your playback devices support those methods of setting it at half-speed. It might also help to mention the audio and video codecs involved, as well as the container. If you don't know, provide the text from MediaInfo.

[larioso]

I'll give it a shot and do a short video at 50p and try and see what happends - if the options are there.

Slowing it to half speed in an NLE requires a full reencode. You specifically asked to retain full quality.

I talked to a guy at Canon and he meant it does not work that well slowing it down.

Canon XA11 have slow motion at 25p as speed so that is way to go. But the newer XA50 is again 50p for slow mo - really weird.
I wonder how much Canon devs are thinking of post production on material and implications on those choices.

JVC GZ-RY980 also do slow motion in any frame rate you set. And you just hold down a button to switch to slow mo in realtime and then release it as you go normal speed again. You follow a bird diving, and move over to slow mo and when landed you go back again.