[FFmpeg-user] DPX bit depth.

tim nicholson nichot20 at yahoo.com
Mon May 11 13:59:07 CEST 2015

On 11/05/15 12:32, Moritz Barsnick wrote:
> On Mon, May 11, 2015 at 10:59:45 +0100, tim nicholson wrote:
>>>> identify -verbose dpx-HD-0001.dpx
>>> Image: dpx-HD-0001.dpx
>>>   Format: DPX (SMPTE 268M-2003 (DPX 2.0))
>>>   Geometry: 1920x1080
>>>   Class: DirectClass
>>>   Type: true color
>>>   Depth: 8 bits-per-pixel component
>>>   Channel Depths:
>>>     Red:      8 bits
>>>     Green:    8 bits
>>>     Blue:     8 bits
> My age-old identify from ImageMagick says:
> [...]
>   Type: TrueColor
>   Endianess: MSB
>   Colorspace: RGB
>   Depth: 16-bit
>   Channel depth:
>     red: 16-bit
>     green: 16-bit
>     blue: 16-bit
> [...]
> I used this to create the file similar to what you did:
> $ ffmpeg -loglevel debug -f lavfi -i testsrc,format=pix_fmts=yuv422p10le -frames:v 1 -c:v dpx ~/tmp/test.dpx -y

Using that same command line I still get a file that GraphicsMagick
claims is 8 bit, *but* like you ImageMagick says 16bit!

>> 25 tbn, 25 tbc" but as graphicsmagik is pretty good I am wondering if it
>> is a case of 8 bit in 10bit becoming 8 bit in 16bit. However i would
>> expect the padding to be in the lsb not msb or the pictures would be
>> very dark.
> "identify" shouldn't worry about whether only 8 MSBs or 8 LSBs of
> available 16 bits are used, it should be your own problem if the image
> is extremely dark. Unless the format has flags to indicate such usage.

Quite, but I was concerned that the somewhere in the process the image
was being down converted to 8 bit. However it looks like its
GraphicsMagick at fault here (I've tried BE and LE with same results).

Interestingly if I execute "convert -depth 16 ...." ImageMagick gives me
a 16bit file from the original , but GraphicsMagick reduces the file to
a real 8 bit one! So its definitely got issues.

Thanks for the confirmation that it s not ffmpeg.

> Moritz
> _[..]

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