This guide is for testing processing speed on hardware configurations with new or old code in the vhs/ld/cvbs decode suits.

hifi-decode is excluded due to faster than real-time being possible with 1-10msps sampling.

7.95 fps - Ryzen 9 7950x (x86) DDR5-4400 128GB config using super-mario-all-stars-video-pal-crosshatch-sample-1m.flac.ldf

14.9FPS - Ryzen 9 7950x (x86) DDR5-4400 128GB config using 16msps 09_wnbc_friends_1997 with --no_resample

16fps - Apple M2 Mac Mini 16GB DDR5 config using 16msps 09_wnbc_friends_1997

8fps - Apple M2 Mac Mini 16GB DDR5 config using Wrapscallion_SMPTEbars_VHS_NTSC_SVO-5800_DdD_gain8.5.ldf with vhs-decode -l 500 --level_detect_divisor 6 --no_resample --use_saved_levels --threads 8

The time command can give you read-out statistics like this

real    154m30.056s
user    0m0.736s
sys     0m1.886s

The above results corresponding to the test samples below (or any from the shared drive so it's easily replicable)

Include what your install is running on bare metal Linux, in WSL2/VMware/VirtualBox on Windows and of course Qemu or Parallels Desktop on MacOS for example.

If your running a compiled version native then this needs to be noted.

As always please get your current builds' commit information, and date/time in dd.mm.yyyy formatting.

CPU/GPU (Make Model & Cooling Solution)

Memory (Amount. Speed and if it's in single, dual or quad channel mode)

Storage (HDD, SATA SSD, NVME SSD etc make model)

If the captures are decoded/encoded to or from SSD/HDD etc ideally always on the fastest drive available.

--threads

While the decoder can only fully use around 4~8 threads this is also a factor dependent on cache and raw single-core speed.

--no_resample

Decodes Input at natively defined sample rate i.g 16msps or 28msps

--use_saved_levels

This skips doing most of the level detect code on each frame and only does it at the start or if there are issues detecting syncs. Provides a speedup in decoding and seems to work okay on captures that only have one single recording of media.

--level_detect_divisor

(Default 2) Experimental (May lower processing time)

1-6 value, 1 every sample, 2 every other sample and so on, Changes vsync serration code only use every nth sample when determining sync/blank levels higher value lower accuracy.

--recheck_phase

Checks chroma phase on each field this can slow performance for colour correctness between multiple tape segments.

--ct

Enables Chroma Trap Intended to reduce chroma interference on the main luma signal, Recommended to use if seeing banding or checkerboarding on the main luma .tbc in ld-analyse.

-l 500 500 Frames

You can pull these files with gdown if you like via the links (Note these may pull entire folders with decoded data too)

40msps SMPTE Bars (30sec) (.ldf) (FLAC)

40msps Nentendo

16msps 09_wnbc_friends_1997

17.6msps

40msps Eden Project

40msps Munday Walking Around (30sec) (.lds & .ldf) (FLAC)

16msps Itewreed Tape 158

Add -f followed by sample rate and -n for NTSC and -p for PAL

While --debug gives a lot more readout information it can cause a drastic slowdown although realistically you always want that extra log information for sanity and testing checks.

As fast as possible (with 16msps raw or FLAC compressed)

vhs-decode -l 500 --level_detect_divisor 6 --no_resample --use_saved_levels --threads 8

As accurate as possible

vhs-decode -l 500 --ct --level_detect_divisor 1 --no_resample --recheck_phase --threads 8

https://stackoverflow.com/questions/25010369/wget-curl-large-file-from-google-drive

• Via Email: harry@opcomedia.com
• Via Document: In the Testing Data folder (In Word/Excel or Docs/Sheets even Plain TXT/PDF)