ffmpeg vmaf skipping some frames towards the end randomly

[tarun-discovery]

I am using following command
ffmpeg -i transcodedA.mp4 -i sourceA.mxf -filter_complex "[0:v][1:v]scale2ref=flags=bicubic[encoded][source];[source]format=pix_fmts=yuv420p,setpts=PTS-STARTPTS[source2];[encoded]setpts=PTS-STARTPTS[encoded1];[encoded1][source2]libvmaf=feature='name=psnr|name=float_ssim|name=float_ms_ssim':n_threads=4:log_fmt=json:log_path=A10-20.json" -f null -

The same command when I run again, the vmaf differs slightly in decimals and some times even by 1%
When I checked deeper by comparing frame level metrics, I noticed following

• both source and transcoded videos have 480 frame count and same fps
• In output frame level metrics one of the execution returned last frame no. as 459, while other as 447. I have attached both files in this ticket.
  Note: vmaf and other metrics were consistent till frame no. 447. So that means it was delta of frames that caused difference in final vmaf.

I do not understand why in both execution frame count didnt went till 480?
Why in both execution end frame count is different. Is it a bug in vmaf lib?

ffmpeg version: n7.0.1
vmaf: v2.3.1

[tarun-discovery]

metrics_winningtime_theriseofthelakersdynastys01e01_20s_fm35s33_chimera-h265-static_hevc_768x432_1091558 (1).json
metrics_winningtime_theriseofthelakersdynastys01e01_20s_fm35s33_chimera-h265-static_hevc_768x432_1091558.json

[XuShiSheng]

你好！邮件已收到，我会尽快回复你--许思焱

[tarun-discovery]

Also when running in debug mode I see following output. If you see Input shows 480 packets read, but output says 466 frames encoded

[vist#0:0/hevc @ 0xaaaafeb531c0] [dec:hevc @ 0xaaaafeb4fc60] Decoder returned EOF, finishing [vist#0:0/hevc @ 0xaaaafeb531c0] [dec:hevc @ 0xaaaafeb4fc60] Terminating thread with return code 0 (success) [fc#0 @ 0xaaaafeb392e0] Filtering thread received EOF [vost#0:0/wrapped_avframe @ 0xaaaafeb82320] Encoder thread received EOF [vost#0:0/wrapped_avframe @ 0xaaaafeb82320] Terminating thread with return code 0 (success) [out#0/null @ 0xaaaafeb49940] All streams finished [out#0/null @ 0xaaaafeb49940] Terminating thread with return code 0 (success) [Parsed_libvmaf_6 @ 0xffff74003690] VMAF score: 69.094762 [fc#0 @ 0xaaaafeb392e0] Terminating thread with return code 0 (success) [out#0/null @ 0xaaaafeb49940] Output file #0 (pipe:): [out#0/null @ 0xaaaafeb49940] Output stream #0:0 (video): 466 frames encoded; 466 packets muxed (205040 bytes); [out#0/null @ 0xaaaafeb49940] Total: 466 packets (205040 bytes) muxed [out#0/null @ 0xaaaafeb49940] video:200KiB audio:0KiB subtitle:0KiB other streams:0KiB global headers:0KiB muxing overhead: unknown frame= 466 fps=9.2 q=-0.0 Lsize=N/A time=00:00:19.39 bitrate=N/A speed=0.384x [in#0/mov,mp4,m4a,3gp,3g2,mj2 @ 0xaaaafeb3a150] Input file #0 (transcoded.mp4): [in#0/mov,mp4,m4a,3gp,3g2,mj2 @ 0xaaaafeb3a150] Input stream #0:0 (video): 480 packets read (2731626 bytes); 474 frames decoded; 0 decode errors; [in#0/mov,mp4,m4a,3gp,3g2,mj2 @ 0xaaaafeb3a150] Total: 480 packets (2731626 bytes) demuxed [AVIOContext @ 0xaaaafeb496a0] Statistics: 2764518 bytes read, 2 seeks [in#1/mxf @ 0xaaaafeb3a2a0] Input file #1 (winning.mxf): [in#1/mxf @ 0xaaaafeb3a2a0] Input stream #1:0 (video): 480 packets read (511717252 bytes); 480 frames decoded; 0 decode errors; [in#1/mxf @ 0xaaaafeb3a2a0] Total: 480 packets (511717252 bytes) demuxed [AVIOContext @ 0xaaaafeb44c30] Statistics: 512219859 bytes read, 6 seeks