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Patrick Cooper

Bitrate settings with certain codecs

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So far, with most of my HD and 4k video editing, I have used the h264 codec. Regarding bitrate settings, I usually set the same bitrate as the original source footage. I am now considering using codecs that use very little compression like prores and photojpeg. Some individuals recommend using a significantly higher bitrate when exporting with these kinds of codecs. Though doesn't that contradict the general advice that you should never use a higher bitrate than your source footage and that there would be no quality benefits in doing so? Actually, I believe there was one individual who reckoned that using a higher bitrate than your source footage could lead to issues with the video quality but I'm not sure if there is any truth to that. What would be the advice here on this matter?

Also bare in mind that I'm not recording on high end pro equipment in an uncompressed format. My source footage (shot with Panasonic G6 and G7 M4/3 cameras) would likely have a fair amount of compression with a low bitrate to begin with. The same with my GoPro footage.

 

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ProRes and JPEG are both capable of applying large amounts of compression. H.264 is capable of applying a very small amount. In general, H.264 is generally used as a distribution codec and will usually be found applying quite stern compression, but camera formats such as XAVC are variants of H.264. Equally, there's nothing very special about ProRes; because it's designed to be simpler it'll generally require higher bitrates to achieve the same quality as most variants of H.264.

Because of all that, there's no simple equation for ideal bitrate. Generally it's better to be more generous when compressing things that have already been compressed, as most camera footage has, since there will already be compression artifacts in it and you don't want to make it worse.

It sounds like what you're looking at doing is transcoding your camera original material to something like ProRes for editing. That's sometimes sensible as it may improve the performance of your edit system, since ProRes is simpler than most of the more heavily-compressed camera formats. That said, every time you recompress something you're losing quality, no matter how much bitrate you throw at it, so only do it if you really need to. Many modern systems will edit directly on camera original material with no problem and there's no point in transcoding it if you don't absolutely need to. 

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The reason why I'm attracted to using codecs like Prores and PhotoJpeg is because I shoot stock footage. And some people reckon that using such codecs as these can increase the chances of sales on a clip. Supposedly, with h264, editors are very limited with the grading that they can apply to a clip whereas with codecs like Prores and PhotoJpeg, they have a lot more flexibility in what they can do without worrying as much about  the quality dropping off or artifacts emerging. Well that's what I keep hearing from the stock footage community. Stock videos with Prores and PhotoJpeg are apparently more attractive to buyers. Though I admit Ive had some decent sales with clips that used h264.

So regarding the bitrate that you would use with Prores and PhotoJpeg, you're confirming that this should be set higher than that of the source footage? Yea it would be good to know if there was some simple formula for working out how much to increase it by. For the people who do use these kinds of codecs, I wonder how they calculate this. 

 

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Every time you re-encode a .h264, you lose quality. Pro Res HQ is considered a "lossless" codec, there is no perceivable loss in quality no matter how many generations you re-encode. 

This is why people master to formats like Pro Res, no matter how good or bad the source is. 

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The footage you capture from your camera is already relatively low bitrate so transcoding it to a codec with a much higher bitrate obviously won't make up for that or increase image quality. ProRes HQ 422 4K @ 24fps has a bitrate of ~750 Mb/s and your GH7 maxes out at 100 Mb/s, I think. If you're simply uploading the clips straight off the memory card, then their original h264 format probably makes the most sense. But if you are trimming or otherwise editing the clips you should export them in a lossless codec like Pro Res HQ (as Tyler mentioned above). The only downside with Pro Res is that you'll end up with much larger file sizes relative to the quality of the source footage, if that is a concern. There are also ways to encode h264 with near-lossless quality and larger file sizes. As far as selling your footage on stock sites goes, advertising as Pro Res HQ will probably get you more clicks from people who might think that the source footage's bitrate is higher than 100 Mb/s.

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Tyler yes, good points. 

Jordan, I have a Pansonic  G7 rather than a GH7. I'm not even aware that they came out with a GH7 in the GH line. Though yes, it has a bitrate of 100mbps. 

All stock videos submitted to the online agencies are trimmed and exported with NLE software and many of the clips have some colour grading applied. I will likely be using Davinci Resolve to export my next bunch of clips. I haven't used this particular software before (I'm currently going through tutorial videos) so I'm not 100% sure on what choices of codecs it has. Though from memory, I think it may offer PhotoJpeg. I don't know if ProRes has been added or not. 

Though I'm still not sure how much I should increase the bitrate with ProRes or PhotoJpeg when exporting my videos. Would it be recommended to double or triple the bitrate in my source footage or use some other formula for working it out?

 

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Exporting from Resolve as ProRes 422 or 422 HQ .mov files should work well for your needs. If you're curious to learn what the bitrate difference are between various ProRes flavors, page 25 of this pdf might be of interest.

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Thank you for that linked article. I note that the bitrate for 4096 x 1260 at 24p for ProRes 422 is 503 mb/s. If I was exporting Panasonic G7 4096 x 1260 24p footage with the ProRes 422 codec in Resolve, would I set the bitrate to 503 mb/s or some other amount?

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In ProRes you won't get a choice; a bitrate is selected as part of the profile selection in the encoder.

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8 hours ago, Phil Rhodes said:

In ProRes you won't get a choice; a bitrate is selected as part of the profile selection in the encoder.

Ah good to know and that makes things convenient. I thought I recall someone mentioning on another forum about manually selecting a high bitrate when using ProRes (unless I'm mistaken.)

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Actually, I do have another query about Davinci Resolve's export options. From what Ive noticed in tutorial videos, I can't see any way of selecting progressive or interlaced. I would prefer progressive video with my exports. How would you know for sure that the video is being exported as progressive?

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Resolve works in progressive. It's part of the reason why people struggle to get MPEG TS streams for broadcast out of resolve. It just can't do interlaced. 

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15 hours ago, Patrick Cooper said:

Thank you for that linked article. I note that the bitrate for 4096 x 1260 at 24p for ProRes 422 is 503 mb/s. If I was exporting Panasonic G7 4096 x 1260 24p footage with the ProRes 422 codec in Resolve, would I set the bitrate to 503 mb/s or some other amount?

Pro Res is a "variable bitrate codec". So it will vary on how much data is needs to be encoded. 

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And Ive just hit a hurdle with Davinci Resolve. Apparently, the version I downloaded is 64bit and my computer uses a 32bit system so they're incompatible. I could only see one version for Windows so I guess that's all there is. Don't ask me why I'm using an ancient 32bit system. Someone who claims to be a computer expert installed it on my pc (even though I told him beforehand that I was planning to edit HD video.) At the time, I didn't realise that 32bit systems are limited to 4GB of RAM. 

Another family member has a laptop which uses 64bit. I could ask her if it's okay to install Resolve on her machine. 

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I think you're going to have to do something about that. I'm not generally a fan of the idea that you have to have the latest toys, but a computer that old is going to put severe limitations on what you can handle.

P

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6 hours ago, Phil Rhodes said:

I think you're going to have to do something about that. I'm not generally a fan of the idea that you have to have the latest toys, but a computer that old is going to put severe limitations on what you can handle.

P

Oh yea I realise I'm overdue for a new computer. When the budget allows, I would like to get a new and reasonably powerful pc one day. 

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This is rather like turning up with a Power Mac and expecting things to work. It's not really a Windows issue.

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