Deinterlacing: 50i footage to 25p or 50p?

Try this for 4:3 PAL .dv in FCP 12.4:

File > New > Project... > Use Custom Settings > Video: Custom, Resolution: 768x576, Rate: 50p, Rendering: Color Space: Standard - Rec. 601 (PAL) > OK > [drag clip to timeline].

Window > Show in Workspace > Inspector [cmd-4] > "i" [at upper right] > Basic to Settings [at lower right] > Field Dominance Override [at upper right] > Lower First or Off (Deinterlace OFF/ON does not seem to make any difference here).

File > Share > HEVC - High Efficiency Video..., Settings > Format: Computer or Apple Devices, Video Codec: HEVC 10-bit [768x576 | 50fps], Action: Save only > Next... > Save.

Or for 4:3 NTSC .dv:

File > New > Project... > Use Custom Settings > Video: Custom, Resolution: 640x480 59.94p, Rendering: Color Space: Standard - Rec. 601 (NTSC) > OK > [drag clip to timeline].

Window > Show in Workspace > Info Inspector [cmd-4] > "i" [at upper right] > Settings [at lower right] > Field Dominance Override [at upper right] > Lower First or Off (Deinterlace OFF/ON does not seem to make any difference here).

File > Share > HEVC - High Efficiency Video..., Settings > Format: Computer or Apple Devices, Video Codec: HEVC 10-bit [640x480 | 59.94fps], Action: Save only > Next... > Save.

Or the same with ffmpeg for 4:3 PAL or NTSC (16:9 needs different scalings and croppings):

ffmpeg -i PAL_4_3.dv -vf bwdif=1,scale=788:576,crop=768:576:10:0,setsar=sar=1/1 -c:v libx265 -crf 18 -preset medium -color_range limited -pix_fmt yuv420p10le -profile:v main10 -x265-params colorprim=5:transfer=1:colormatrix=6:range=limited -timecode 00:00:00:00 -tag:v hvc1 -c:a aac_at -b:a 128k PAL_dv_libx265_to_10bit_limited_5-1-6.mp4

ffmpeg -i NTSC_4_3.dv -vf bwdif=1,scale=648:480,crop=640:480:4:0,setsar=sar=1/1 -c:v libx265 -crf 18 -preset medium -color_range limited -pix_fmt yuv420p10le -profile:v main10 -x265-params colorprim=6:transfer=1:colormatrix=6:range=limited -timecode '00:00:00;00' -tag:v hvc1 -c:a aac_at -b:a 128k NTSC_dv_libx265_to_10bit_limited_6-1-6.mp4

Ian R. Brown wrote:

The main videos I will be using it on are 1080 so I assume I just swap those numbers.

In interlaced material I have usually avoided vertical scaling (or used integers such as in PAL height 2*576 = 1152) because it might introduce interlacing artifacts.

But now I tried FCP with 4:3 PAL and NTSC .dv input to "bob deinterlaced" double fps 1920x1080 and and in both the output was OK. FCP automatically padded left & right sides with black and scaled rectangular .dv pixels to square pixels so circles remained circles in PAL, NTSC output is very slightly squeezed horizontally.

As for ffmpeg, I don't use that directly but I believe it is the basic engine for Handbrake and Shutter Encoder, so presumably those could be used.

I have used ffmpeg because I have rectangular to square pixel workflow as well as color triplets, quality settings etc verified there. AFAIR the last time I could not 100% replicate all that in Handbrake GUI. BTW it is possible to paste ffmpeg commands to Shutter Encoder but it is easier to paste them to the Terminal anyway.

You're running on a commonly believed mistake. 60i is not two half-frames per second, it is one half frame every 1/60 of a second (or "field"). Thus, 60i is one field every 1/60 of a second, thus two fields are shot at two different times. Thus the combing effect. Thus, it is more technically accurate to convert 60i to 60p rather than 30p. Neither way "combines" fields to make up a frame, since those two fields were NOT shot at the same time. Same for 50i.

With Handbrake (Version 1.11.2) settings below I get about the same output from 4:3 PAL .dv input as via Terminal with ffmpeg with libx265 CPU encode, or much faster (but slightly lower quality with the same output size) ffmpeg with Apple's VideoToolbox hardware-accelerated encode.

Notice that .dv shot in shutter speeds 1/25 s or slower are essentially progressive, i.e. both fields are the same so there are no comb lines, and there is no benefit in encoding interlaced 25i to double fps 50p because then every other 50 fps frame is the same.

Handbrake custom settings:

Summary tab:

Preset: use "Fast 576p25" as a starting point, then modify as follows:

Format: MP4

Dimensions tab:

Cropping: Custom 8 + 8 pixels from left & right [correct 9 + 9 is not possible]

Resolution Limit: Custom 768x576

Allow Upscaling: ON

Final Dimensions: Automatic OFF, Display Size: 768x576 [Return]

(Anamorphic: Automatic)

(Pixel Aspect: 1:1)

(Scaled Size: 768x576)

(Optimal Size: ON)

(Storage Size: 768x576)

(Aspect Ratio: 4:3)

Filters tab:

Deinterlace: Bwdif, Preset: Bob

Chroma Smooth: Medium, Tune: Medium

Color Space: BT.601 EBU

Video tab with libx265 CPU encode:

Video Encoder: H.265 10-bit (x265)

Framerate (FPS): 50

Constant Framerate ON

Color Range: Limited

Quality: Constant Quality RF 18-28 (default 28)

Encoder Options: Preset: Slow-Medium (default Medium)

Profile: main10

Or Video tab with much faster (but lower quality with the same output size) Apple's VideoToolbox hardware-accelerated encode:

Video Encoder: H.265 10-bit (VideoToolbox)

Framerate (FPS): 50

Constant Framerate ON

Color Range: Limited

Quality: Constant Quality CQ 58

Encoder Options: Preset: quality

Profile: main10

Audio tab:

Codec: AAC (CoreAudio)

Bitrate: 128

Shutter speed does not change the timing of the fields/frames, so they are never shot at the same time, period.