[FFmpeg-user] Converting BT2020 HVEC Videos to H.264 without Color Washout

[pehache]

Le 26/03/2021 à 00:55, Craig L. a écrit :
> Sorry. I don't think I responded to this correctly before.
> 
> 
> I think I tried exactly that based upon this stackoverflow question:
> 
> https://stackoverflow.com/questions/64981984/ffmpeg-transcode-uhd-h265-to-sdr-h264-without-color-loss 
> 
> 
> The example in that post uses this command:
> 
> |ffmpeg -i 4K.ts -vf 
> zscale=t=linear:npl=100,format=gbrpf32le,zscale=p=bt709,tonemap=tonemap=hable:desat=0,zscale=t=bt709:m=bt709:r=tv,format=yuv420p 
> -c:v h264 -crf 19 -preset ultrafast output.mp4 |
> 
> Which I thought might be my solution but when I tried it, it ended up 
> making the video too red.
> 

Same here, much too red output in the shadows.

(I'm leaving the rest the rest of the discussion below, as it is an old one)





> 
> On 3/25/21 4:09 PM, Pavel Koshevoy wrote:
>> On Thu, Mar 25, 2021 at 9:27 AM Craig L. <ffmpeg at trafficality.com> wrote:
>>
>>> I recently started finding certain videos were washing out upon H.264
>>> conversion.
>>>
>>>
>>> After doing some research I found that if I added -color_primaries
>>> bt2020 to the command, the color would come out correctly, but ONLY if
>>> the video was played in Quicktime.  When played in Chrome, it would look
>>> washed out.
>>>
>>> Here is a link to a screengrab showing the video in quicktime on the
>>> left and in Chrome on the right.  Same video.
>>>
>>>
>>> *https://snipboard.io/N8nYv0.jpg* <https://snipboard.io/N8nYv0.jpg>
>>>
>>>
>>>
>>>
>>> After much research I can't figure out how to handle this?
>>>
>>> What is the correct way to convert these videos that I suppose are 10
>>> bit HDR  into H.264 so that they will play correctly in Chrome, etc.
>>>
>>>
>>>
>>> This is my current command:
>>>
>>> /usr/local/bin/ffmpeg  -i "156237-Video2.mov"   -filter_complex
>>> "scale=480:270"  -color_trc smpte2084 -color_primaries bt2020 -c:v
>>> libx264 -profile:v high -pix_fmt yuv420p -level 5.1 -preset ultrafast
>>> -movflags faststart       -vsync 2  -c:a aac -b:a 128k     -y
>>> 156237-Video2.mov-16-9-1616621202.mp4
>>>
>>>
>>>
>>>
>>>
>> For best possible player compatibility you really need to convert from
>> HDR10 to SDR (bt709).
>>
>> To do that you need to use either colorspace or zscale ffmpeg filter.  
>> The
>> colorspace filter didn't support HLG the last time I checked, but that
>> wouldn't matter if your source is HDR10, not HLG.
>> Since you'd be converting from high dynamic range to standard dynamic 
>> range
>> you would also need to use the tonemap filter.
>>
>> There is probably a LUT file somewhere that implements HDR10 -> BT709 
>> color
>> space conversion and tone mapping in one step, skipping 
>> zscale/tonemap.  If
>> you had such LUT you could use it with lut3d filter.
>>
>> Pavel.
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