Trimming Video at Specific Frames

[caivs]

Hello, I do speedruns and it is important to be able to make videos that start and end on the exact frame that I want. Normally I use AmarecTV to record lossless AVI video files and then I put them into Aviutl to encode videos to share. When I do this I have to correct the aspect ratio and scale. I've admittedly never had a problem having the videos start and stop on the correct frames but now I'm trying something different and using OBS to get raw recordings that are already the correct aspect ratio and scale (trying to make my life easier and get better looking videos). With OBS I don't have the option to record AVI, so I have been using MP4. My goal is to be able to trim these MP4 files without re-encoding them because the reason I'm trying to use OBS is because of the different quality I can get vs AmarecTV. I've tried using Losslesscut and avideremux to try and accomplish this but I learned that I wasn't able to select the specific frame to trim without re-encoding at becuase it needs to be a keyframe, or I or P or whatever. Is there a way to do this or is it just an inherent thing with mp4 files? I'm a noob.

[jagabo]

You need a smart editor like VideoRedo, Solveigmm, or Tmpgenc Video Mastering Works. Those will allow cuts on any frame and only reencode the cut GOPs -- a few seconds at the beginning and end.

[poisondeathray]

Another option is to recorded intra (every frame is a keyframe) , then you can cut on any frame with avidemux in "copy" mode.

The quality will generally be lower at a given filesize or bitrate , unless you are using very high bitrates. In other words, you'd usually need to use higher bitrates to get similar quality as default settings

If you want to try this , I think only x264 supports it for OBS, the other HW encoders do not. In the x264 options box enter "keyint=1" (without the quotes)

[Cornucopia]

If you are doing speedruns, and you are recording on the SAME computer that you are performing with, you really should be capping to a higher bitrate I-frame lossless intermediate anyway. Why?
Your performance is likely to be CPU/GPU intensive, but not storage pipeline intensive. So you want to balance that in the recording with a codec that ISN'T CPU/GPU intensive, but (assuming you have the speed/bandwidth) IS more storage pipeline intensive. That's a digital intermediate lossless format. E.g. HuffYUV, Lagarith, UT, MagicYUV, etc. Or even possibly a near-lossless format, such as Cineform, DNxHD, ProRes, Edius/GV HQX, etc. if the quality is still acceptable to you and you need a somewhat lower than highest bitrate.

Then you would only be doing a single pass of a full lossy encode to something like h264, after editing/trimming.
Also, you wouldn't be limited to using only SmartRendering editors.
And your quality would be the best possible with your setup.


Scott

[caivs]

You need a smart editor like VideoRedo, Solveigmm, or Tmpgenc Video Mastering Works. Those will allow cuts on any frame and only reencode the cut GOPs -- a few seconds at the beginning and end.

I tried VideoReDo and Solveigmm and neither of them could even open my mp4s :/ what the heck.

Another option is to recorded intra (every frame is a keyframe) , then you can cut on any frame with avidemux in "copy" mode.

The quality will generally be lower at a given filesize or bitrate , unless you are using very high bitrates. In other words, you'd usually need to use higher bitrates to get similar quality as default settings

If you want to try this , I think only x264 supports it for OBS, the other HW encoders do not. In the x264 options box enter "keyint=1" (without the quotes)

This worked! Thank you very much. I'm using crf=0 and didn't really notice any difference in quality.

If you are doing speedruns, and you are recording on the SAME computer that you are performing with, you really should be capping to a higher bitrate I-frame lossless intermediate anyway. Why?
Your performance is likely to be CPU/GPU intensive, but not storage pipeline intensive. So you want to balance that in the recording with a codec that ISN'T CPU/GPU intensive, but (assuming you have the speed/bandwidth) IS more storage pipeline intensive. That's a digital intermediate lossless format. E.g. HuffYUV, Lagarith, UT, MagicYUV, etc. Or even possibly a near-lossless format, such as Cineform, DNxHD, ProRes, Edius/GV HQX, etc. if the quality is still acceptable to you and you need a somewhat lower than highest bitrate.

Then you would only be doing a single pass of a full lossy encode to something like h264, after editing/trimming.
Also, you wouldn't be limited to using only SmartRendering editors.
And your quality would be the best possible with your setup.


Scott

This seems interesting to me but most of it is over my head. I'm playing on a Nintendo 64 and capturing the gameplay so I'm not playing a game with the GPU or anything on the computer and Lagarith actually is the codec that I use with AmarecTV to make raw recordings. Unfortunately I can't use it with the other program OBS. I could just put the mp4s into aviutl and trim them that way, because it works, but it changes the way the footage looks which defeats the purpose of switching to OBS from AmarecTV in the first place.

[jagabo]

You need a smart editor like VideoRedo, Solveigmm, or Tmpgenc Video Mastering Works. Those will allow cuts on any frame and only reencode the cut GOPs -- a few seconds at the beginning and end.

I tried VideoReDo and Solveigmm and neither of them could even open my mp4s :/ what the heck.

What audio and video codecs did you use?

<edit>
I see you changed the earlier post and are now happy with x264, CRF=0, keyint=1.
</edit>

[poisondeathray]

This worked! Thank you very much. I'm using crf=0 and didn't really notice any difference in quality.

crf=0 is lossless mode, so the quality is always the same

But when you use intra encoding, the filesize will increase to compensate, because there is no temporal compression being used.