transcode: same size as hires file but half the bitrate (and/or: why is duration of proxy twice as long)?

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    • transcode: same size as hires file but half the bitrate (and/or: why is duration of proxy twice as long)?

      New here. I can read German but prefer writing English. Hope that's ok!

      I have a VU Uno 4K SE.

      I noticed the transcoded proxy files are as big as the hires files. With my test recording of 10 minutes: 1 GB.

      The bitrate of the proxy is less than 50% of the hires.
      - hires is MPEG TS with H.264 high profile 1920x1080 @ 25 fps, bitrate 14474 kb/s
      - proxy is MPEG TS with H.264 baseline 720x480 @ 30 fps, bitrate 6927 kb/s

      Duration of my test file is 00:10:00.52, the expected filesizes are:
      - hires: (10*60*14474) / 1024 / 1024 / 8 = 1.03 GB --> as expected
      - proxy: (10*60*6927) / 1024 / 8 = 507 MB --> actual file is also 1.03GB

      What is strange: the reported duration of the proxy file is not 10 but 20 minutes (and the start differs).
      With that reported duration the filesize is correct: ((20*60 + 44) *6927) / 1024 / 1024 / 8 = 1.03GB

      So, why is the duration twice as long?



      Source Code

      1. Input #0, mpegts, from 'hires.ts':
      2. Duration: 00:10:00.52, start: 115.187867, bitrate: 14474 kb/s
      3. Program 19401
      4. Stream #0:0[0x7d1]: Video: h264 (High) ([27][0][0][0] / 0x001B), yuv420p(tv, bt709, top first), 1920x1080 [SAR 1:1 DAR 16:9], 25 fps, 50 tbr, 90k tbn, 50 tbc
      5. [...]
      6. Input #0, mpegts, from 'proxy.ts':
      7. Duration: 00:20:43.71, start: 72624.739922, bitrate: 6927 kb/s
      8. Program 1
      9. Stream #0:0[0x11]: Video: h264 (Baseline) ([27][0][0][0] / 0x001B), yuv420p(progressive), 720x480 [SAR 8:9 DAR 4:3], 29.97 fps, 30 tbr, 90k tbn, 59.94 tbc
      10. Stream #0:1[0x12]: Audio: aac (LC) ([15][0][0][0] / 0x000F), 48000 Hz, stereo, fltp, 130 kb/s
      11. wget "http://vuuno4kse:8002/file?file=${file}" -O proxy.ts
      12. [...]
      13. Length: 1086537728 (1.0G) [video/mpeg]
      14. [...]
      15. du -sm *.ts
      16. 1041 hires.ts
      17. 1028 proxy.ts
      Display All


      Related, when using wget, the transfer speed is max 900 KB/s (scp of the hires file is in my case 17 MB/s). Is that a limit of the transcoder?
      And I get many connection drops - especially near the end (that wget can deal with just fine), even though both STB and server are connected by ethernet.
    • and to be sure, when I stream the content (e.g. VLC), it streams at the expected 7000 kb/s.

      Should I use a different way to download the proxy content?
      Currently using e.g. wget:
      wget "http://vuuno4kse:8002/file?file=${file}" -O proxy.ts