A point on H264 and Prores

Hello,

I know the subject is not new. But I'd like to talk about my own experience.
I have read a lot before starting to work with both of them format (a few years now) and basically the professional approach was:

always convert H264 to Prores before editing for two main reasons :
- one : your editor will have to use more CPU with H264, because it will have to decompress the clips before reading/displaying them.
- second : when you will grade, you will work with a lot less color information within a restrain colorspace with H264 than with Prores and the correction/grade will be more difficult and less precise.

Correct me if I am wrong but these are the two only (and important) arguments there is, right ?

Now, as for the first argument. Converting to Prores requires a lot more disc space than H264. This is something to keep in mind first. Second, no conversion is absolutely lossless meaning the fewer conversion the better. But, if my computer is fast enough, if Resolve for example, reads all H264 clips well without dropping frame when played back, then there is no reason not to edit with H264.
This is a statement based on my own experience, if you have any valid argument (quality-wise for ex), please correct me.

As for the second argument. Yes there is no comparison, when color correcting grading, Prores will always perform better, but then I have a question. Say on an entire edit (done with H264) I have a few clips that need to be corrected, can we just convert to Prores the clips that need to be corrected and export the whole H264+Prores clips at once when done ?

Thanks for your input.
Alexandre

always convert H264 to Prores before editing for two main reasons :
- one : your editor will have to use more CPU with H264, because it will have to decompress the clips before reading/displaying them.

All codecs have to be decompressed but inter-frame decompression is harder when you edit video because frames have to be decompressed by using data from neighboring frames.

The reason you want to transcode H.264 is because H.264 is often used with inter-frame compression. But this is not always true, as you can encode H.264 with all-intra settings as well. Using H.264 all-intra makes it similar to ProRes, they are both DCT based CODECs.

- second : when you will grade, you will work with a lot less color information within a restrain colorspace with H264 than with Prores and the correction/grade will be more difficult and less precise.

This is not correct. Transcoding a video will always reduces the video quality although the difference is minimum for high bitrate encodings. The idea that ProRes makes things better video quality wise is absolutely untrue.

Now, as for the first argument. Converting to Prores requires a lot more disc space than H264. This is something to keep in mind first. Second, no conversion is absolutely lossless meaning the fewer conversion the better. But, if my computer is fast enough, if Resolve for example, reads all H264 clips well without dropping frame when played back, then there is no reason not to edit with H264.

If your computer can handle it you do not need to transcode.

As for the second argument. Yes there is no comparison, when color correcting grading, Prores will always perform better, but then I have a question. Say on an entire edit (done with H264) I have a few clips that need to be corrected, can we just convert to Prores the clips that need to be corrected and export the whole H264+Prores clips at once when done ?

Well, as I wrote before, this is just not true, ProRes, or any other codec, does not make a source any better than it already is.

All-intra has the advantage to make the editing smoother performance wise but there are also disadvantages. With the same bitrate an inter-frame encoding will generally be superior to an all-intra encoding.

ProRes is a great codec, but is not any more special than other codecs. For editing it is better to use an all-intra codec, this could be ProRes but it could also be something else.

I am aware that some people have the impression that ProRes is a codec covered with gold but while it is a robust codec and a standard for many companies it is technically just like any other codec.

What you have read/been told are horrible generalizations unless put into context.

It seems many professionals cannot differentiate between what a codec is capable of, and how its implemented by a devise manufacture. A lot of people knock h.264, because they have only ever worked with h.264 footage out of low end consumer grade devises, that are using it to make small video files as cheaply as possible.

As a codec H.264 supports 8 to 14 bit color, 4:20 to 4:4:4 chroma subsampling, compression that ranges from mush to lossless, and both inter and intra frame compression.

If you need to transcode h.264 footage or not, depends on what type of footage it is. If it's intra frame compression, you are most likely wasting your time and disk space by doing so.

My statements were not really mine but those of the many online documentation and discussions.
I wanted to confirm my doubts (which were in fact a lack of knowledge) of those assumptions.
I did not know about the importance of all-intra frame (which I am using).
Thank you for your precise answers.

I would say you rather want to ask such a questions on forums like this one (where it can be discussed and not in form of a statement of a single person).
My advice is to stay away from youtubers, as in most cases they are simply wrong and keep repeating things which they have heard/read (which are quite often just a rumours), but don't really understand. Unfortunately there is so much "crap" on youtube these days regarding post-production. There is huge difference of being youtuber and experienced post-production engineer, really huge Problem is that what you watch/hear comes in 90% from 1st group, which is no really a good source of reliable information.

As a non professional user of Resolve, I will relate my own experiences when editing for YouTube.
I shoot 8bit MP4 1080 50p video at 35Mbps. Resolve on my system has no problem working with this so I don't transcode to any other format. Any transforms I do are limited to straightening a shot and zooming in slightly to fill the frame, and I also add titles and crossfades etc. Again no performance problems with these. I tend to do simple grading and colour correction again without a performance hit. When it comes to rendering I use h.264 in a .mov container still at the 35Mbps of the original footage and run the render at 25% speed to help with the processing. Unlike some I have no problems with the final video quality.
Recently I have been experimenting with editing and rendering the HD footage in a UHD timeline to combat the artifacts that can be introduced by YouTubes re-compression with great success. This time I render at 60Mbps.
Make of this what you will. All I can say is it works for me.

You can see an example here.

Hi Charles

If you right-click your mouse on your movie on Youtube -
choose statistics for nerds - you can see that when uploading UHD,
the movie will be encoded as vp9 - by HD 1080 encoded as avc!

Hi Charles

If you right-click your mouse on your movie on Youtube -
choose statistics for nerds - you can see that when uploading UHD,
the movie will be encoded as vp9 - by HD 1080 encoded as avc!

It's always re-encoded, no matter what resolution or codec you upload.

enter any YouTube video url into this page and you can see all the resolutions, and codecs it's been reencoded for.
https://www.h3xed.com/blogmedia/youtube-info.php

"It's always re-encoded, no matter what resolution or codec you upload."

Yes, everybody knows ....

Agree with you 100% Ole. The main reason is that YouTube allocates a higher bitrate to UHD so at 4k playback artifacts such as blocking are minimised. So the video I linked to yields this.

Ok thank you for all these advises.
I have finished to work on my colors... on original H264 clips.
Now for the export, what do you suggest I do :
- I export in prores and use dedicated software such as Apple Compressor for compression ?
- I export straight in H264, whit what settings if I want to keep the same quality (for that export only) ?
Thanks a lot.
Alexandre

Ok thank you for all these advises.
I have finished to work on my colors... on original H264 clips.
Now for the export, what do you suggest I do :
- I export in prores and use dedicated software such as Apple Compressor for compression ?
- I export straight in H264, whit what settings if I want to keep the same quality (for that export only) ?
Thanks a lot.
Alexandre

I would say that depends what you want to do with it and what your workflow is.

Key thing to remember is that any time your encode a video the quality goes down (except for lossless encoding).

If you encode with sufficient bitrate (say twice the original bitrate or doubling that when using all-intra) the loss is minimal.

I would say that depends what you want to do with it and what your workflow is.

Well I have edited and graded H264 clips straight from a canon 5DMK3 into Davinci.
Now I need to export the whole in the best format I can for TV broadcast.

Key thing to remember is that any time your encode a video the quality goes down (except for lossless encoding).

Is prores 422HQ lossless encoding ?

Thank you

Now I need to export the whole in the best format I can for TV broadcast.

Obtain the specs from the TV station and encode accordingly.

Is prores 422HQ lossless encoding ?

No.

prores 422 hq is used by both Netflix and Amazon.
Its good enough

Now I need to export the whole in the best format I can for TV broadcast.

They all have their preferred delivery formats- can be AVC-I, ProRes, DNxHD, XDCAM HD etc.
For brodcast ProRes/DNxHD is definitely good enough. In most case they are happy with XDCAM HD (50mbit MPEG2). Broadcast is not really about quality, but quantity.
To avoid problem the best is ask what they want.