Memory leak in zscale

[Anton1699]

Summary of the bug:

I was very happy to see slice threading support added to the zscale-filter but it appears to have caused a memory leak. The following command used just over 12 GiB of memory before crashing. The full report is attached.

How to reproduce:

% ffmpeg -hide_banner -nostdin -report -i file.mkv -noautoscale -filter_complex [0:0]zscale=pin=bt709:min=gbr:tin=iec61966-2-1:rin=pc:agamma=false:d=error_diffusion:f=bilinear:p=bt709:m=bt709:t=bt709:r=tv:c=left,format=yuv420p[out] -map [out] -f null NUL
ffmpeg started on 2022-03-04 at 12:57:53
Report written to "ffmpeg-20220304-125753.log"
Log level: 48
Input #0, matroska,webm, from 'file.mkv':
  Metadata:
    ENCODER         : Lavf59.17.101
  Duration: 00:17:36.69, start: 0.000000, bitrate: 74212 kb/s
  Stream #0:0: Video: h264 (High 4:4:4 Predictive), gbrp(pc, gbr/bt709/iec61966-2-1, progressive), 1448x1080 [SAR 1:1 DAR 181:135], 29.97 fps, 29.97 tbr, 1k tbn (default)
    Metadata:
      ENCODER         : Lavc59.20.100 h264_nvenc
      DURATION        : 00:17:36.689000000
  Stream #0:1: Audio: flac, 48000 Hz, stereo, s16 (default)
    Metadata:
      ENCODER         : Lavc59.20.100 flac
      DURATION        : 00:17:36.577000000
Stream mapping:
  Stream #0:0 (h264) -> zscale:default
  format:default -> Stream #0:0 (wrapped_avframe)
Output #0, null, to 'NUL':
  Metadata:
    encoder         : Lavf59.17.102
  Stream #0:0: Video: wrapped_avframe, yuv420p(pc, gbr/bt709/iec61966-2-1, progressive), 1448x1080 [SAR 1:1 DAR 181:135], q=2-31, 200 kb/s, 29.97 fps, 29.97 tbn
    Metadata:
      encoder         : Lavc59.21.103 wrapped_avframe
Error while filtering: Cannot allocate memory8:22.40 bitrate=N/A speed=6.21x
Failed to inject frame into filter network: Cannot allocate memory
Error while processing the decoded data for stream #0:0
Conversion failed!

[Anton1699]

compressed report

[Elon Musk]

Fixed in 779ae049b26ad0ea878bfc4a3a2326308b8f6b13