interlaced conversion stuttering

[fullhdfan]

hi !

I have a problem with the conversion of the recordings from my "old" JVC HM200 camera (2010,"pre-smartphone era"). I want to archive a couple of videos
in order to save some space on the harddisk. I've done the conversion using x264/Avidemux. Given the chip quality of that time and the questionable high quality(17Mbps) and ultrahigh quality(22Mbps) modes of that camera, the converted files resulted have 50% file size or less than the original, allowing me to save some extra 20GB.
But there is a problem ! The videos are interlaced, lots of them have a lot of motion, the converted files showing less stuttering on my pc, but more on my tv.
The original file shows stuttering on the tv as much, but (interestingly) plays very smoothly on my PC.

these are the original file infos:

Format                         : Matroska
Format version                 : Version 4
File size                      : 790 MiB
Duration                       : 4 min 56 s
Overall bit rate mode          : Variable
Overall bit rate               : 22.4 Mb/s
Encoded date                   : UTC 2020-03-09 11:27:31
Writing application            : [url=https://www.videohelp.com/software/MKVToolNix]mkvmerge[/url] v19.0.0 ('Brave Captain') 32-bit
Writing library                : libebml v1.3.5 + libmatroska v1.4.8

Video
ID                             : 1
Format                         : AVC
Format/Info                    : Advanced Video Codec
Format profile                 : High@L4
Format settings                : 2 Ref Frames
Format settings, CABAC         : No
Format settings, Reference fra : 2 frames
Format settings, GOP           : M=2, N=12
Codec ID                       : V_MPEG4/ISO/AVC
Duration                       : 4 min 56 s
Bit rate mode                  : Variable
Bit rate                       : 22.1 Mb/s
Maximum bit rate               : 22.6 Mb/s
Width                          : 1 920 pixels
Height                         : 1 080 pixels
Display aspect ratio           : 16:9
Frame rate mode                : Variable
Frame rate                     : 50.000 FPS
Original frame rate            : 25.000 FPS
Color space                    : YUV
Chroma subsampling             : 4:2:0
Bit depth                      : 8 bits
Scan type                      : Interlaced
Scan type, store method        : Separated fields
Scan order                     : Top Field First
Bits/(Pixel*Frame)             : 0.213
Stream size                    : 779 MiB (99%)
Default                        : Yes
Forced                         : No

Audio
ID                             : 2
Format                         : AC-3
Format/Info                    : Audio Coding 3
Commercial name                : Dolby Digital
Codec ID                       : A_AC3
Duration                       : 4 min 56 s
Bit rate mode                  : Constant
Bit rate                       : 256 kb/s
Channel(s)                     : 2 channels
Channel layout                 : L R
Sampling rate                  : 48.0 kHz
Frame rate                     : 31.250 FPS (1536 SPF)
Compression mode               : Lossy
Delay relative to video        : 40 ms
Stream size                    : 9.04 MiB (1%)
Service kind                   : Complete Main
Default                        : Yes
Forced                         : No

and the converted one's:

Format                         : Matroska
Format version                 : Version 4
File size                      : 197 MiB
Duration                       : 4 min 56 s
Overall bit rate               : 5 570 kb/s
Writing application            : Lavf58.20.100
Writing library                : Lavf58.20.100
ErrorDetectionType             : Per level 1

Video
ID                             : 1
Format                         : AVC
Format/Info                    : Advanced Video Codec
Format profile                 : High@L4
Format settings                : CABAC / 4 Ref Frames
Format settings, CABAC         : Yes
Format settings, Reference fra : 4 frames
Codec ID                       : V_MPEG4/ISO/AVC
Duration                       : 4 min 56 s
Width                          : 1 920 pixels
Height                         : 1 080 pixels
Display aspect ratio           : 16:9
Frame rate mode                : Constant
Frame rate                     : 25.000 FPS
Original frame rate            : 50.000 FPS
Color space                    : YUV
Chroma subsampling             : 4:2:0
Bit depth                      : 8 bits
Scan type                      : MBAFF
Scan type, store method        : Interleaved fields
Scan order                     : Top Field First
Writing library                : x264 core 159
Encoding settings              : cabac=1 / ref=2 / deblock=1:0:0 / analyse=0x3:0x133 / me=umh / subme=7 / psy=1 / psy_rd=1,00:0,00 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=3 / lookahead_threads=1 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=tff / bluray_compat=0 / constrained_intra=0 / bframes=3 / b_pyramid=2 / b_adapt=1 / b_bias=0 / direct=1 / weightb=1 / open_gop=0 / weightp=0 / keyint=250 / keyint_min=25 / scenecut=40 / intra_refresh=0 / rc_lookahead=40 / rc=crf / mbtree=1 / crf=22,0 / qcomp=0,60 / qpmin=10 / qpmax=51 / qpstep=4 / ip_ratio=1,40 / aq=1:1,00
Default                        : Yes
Forced                         : No
DURATION                       : 00:04:56,140000000

Audio
ID                             : 2
Format                         : AAC LC
Format/Info                    : Advanced Audio Codec Low Complexity
Codec ID                       : A_AAC-2
Duration                       : 4 min 56 s
Channel(s)                     : 2 channels
Channel layout                 : L R
Sampling rate                  : 48.0 kHz
Frame rate                     : 46.875 FPS (1024 SPF)
Compression mode               : Lossy
Delay relative to video        : -80 ms
Default                        : Yes
Forced                         : No
DURATION                       : 00:04:56,143000000

i have tried the combination of the following params:

CRF 20-23(no noticeable loss in quality) or
CBR 12,5 Mbps(the same)
max. reference frames 1,2,3 and 4
hexagonal and uneven multi-hexagonal search
interlaced-TFF

the rest are the x264's default params.

Another thing which confuses me is in the video properties:
format settings, reference frames: 4
encoding settings ref=2

is it the same parameter ?

Thanks.

[Sharc]

Maybe the problem comes from the Variable Frame Rate of the 'original' (reported as 50/25fps). Is the original file from your camera really an .mkv?

[davexnet]

Possibly the TV doesn't like the MBAFF scan type (just a guess). I played them on my 2017 LG 4k TV
and they both looked good.

Here's a small section converted to Progressive @ 50 fps, encoded in Vidcoder

[fullhdfan]

@Sharc

Thanks for the tip ! Indeed, the players don't like the confusing 25/50fps. I don't know where does it come from. The original file from the camera is a .ts file. I changed the original container to mkv in order to save some space on hdd because ts files have a large overhead. I recorded a test video today and changed the container to mkv with mkvtoolnix. I have also converted the original test file and saved it to a .mkv and .mp4 container using avidemux. All containers - the original recording in the .mkv container and the converted ones - have such confusing infos.
I have used the "resample fps" filter from avidemux as dummy, set fps to 25 and the problem is GONE. The files play as the original recording on my PC (with an almost unnoticeable stuttering, probably because of the graphic card or 60 hz monitor rate), but perfectly(very smoothly) on my tv.