Background:
I normally use an iMac-M3 for Channels DVR, with a "back-up system" of a Raspberry Pi.
I'm retired, but involved in a couple of pro bono software and hardware projects. A few of months ago, I needed to use the iMac for a project where I needed to turn it on and off regularly at the times that Channels DVR was running. One option that I looked at was buying a small Intel N5 computer as my full time DVR. I didn't - The reasons are below...
The pro bono work gave me access to Raspberry Pi boards (RPi); associated hardware including an old 2GB R-Pi4; 2, 4, and 8GB R-Pi5s; HDDs, M2.SSDs, USB-SSDs; and various cases and accessories. Based on this, decided that I would evaluate what could work for us.
Currently we have >1TB of recordings. We don't watch much live TV, as we record 4-5 hours each day and watch it later. Our useage indicates that 2TB of external storage is needed, and I want to "set and forget". The DVR runs as a background service on the iMac. I don't use Remote Streaming (If I'm away, I will have downloaded to an iPad, or will watch live internet streaming). So, we don't need a Hardware Transcoder.
I prefer ExFAT for transferrable external storage, with the Channels DVR application on an internal drive. The external storage includes DVR databases, logs, imports etc., and is backed up with rsync every night accross our network. This allows a quick swap to another system if needed.
Testing:
The results below were 3 runs averaged with a 2TB Crucial SSD. The Pi5 was initially booting from a R-Pi 256 M.2 SSD with a Pi5 case and an Active Cooler.
Comskip (mins). All with 2 Cores iMac RPi-4 RPi-5
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TV Episode 12 markers 45 min 0.9 6.5 2.9
TV Movie 24 markers 165 min 8.4 60.4 28.8
Further experiments with the RPi-5 and a 2TB WD HDD gave a time of 31.5 mins with the TV Movie. The Official R-Pi 32GB MicroSD finished in 32 mins. The Crucial SSD with the MicroSD gave a time of 29.4 mins.
Cost and Geekbench scores of equipment:
Item US$ AU$
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Raspberry Pi 5/2GB $50 $82
Official Pi microSD Card, 64GB $11 $16
Raspberry Pi 27W Power Supply $14 $21
Flirc Raspberry Pi 5 Case $18 $26
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TOTAL $93 $145
Raspberry Pi5 Geekbench
Singlecore @ 2.4 GHz: 764
Multicore @ 2.4 GHz: 1604
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Beelink MINI S12 N95 256GB SSD $169 $265
Intel Processor N95 Geekbench
Singlecore @ 3.2 GHz: 1028
Multicore @ 3.2 GHz: 2649
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Apple iMac M3 All-In-One $1,400
Geekbench CPU Benchmark Scores
Singlecore @ 4.1 GHz: 3040
Multicore @ 4.1 GHz: 11693
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My Observations:
Channels uses little memory and CPU when watching and recording. The only time that the equipment works hard is when running Comskip - 2GB of RAM with Bookworm 64-bit Light seems adequate.
The RPi-5 runs hotter than the RPi-4. It is summer here, and the fans in the standard RPi5 cases are often running when idle, with a temperature of ~45-50C. When comskip is running, the CPU temp could go up to 60C. Using a RPi "heat sink" case (no fan) like the FLIRC is feasible if the CPU temperature is not too high. When idling, the 2GB RPi-5 runs about 14C warmer than ambient, the RPi-5 with 4 or 8GB of RAM run ~4C warmer than the RPi-5 2GB. With the 2GB RPi-5 the maximum temperature recorded with the FLIRC cases was 68.2C (Recording 2 x 2K and 1 x 1K stream whilst watching a 4K stream live on an Apple 4K TV and streaming a previously recorded movie on an iPad Pro). The live recording were scheduled to finish at the same time (Comskip took a total of <35 mins) - After these recordings a 4K and a 2K program immediately followed. After hitting peak temperature, the Pi cooled by 16C within 6 minutes. Just to be on the safe side I added:
temp-limit=70
to: /boot/firmare/config.txt
I have not seen any obvious problems or CPU throttling.
Channels DVR and Bookworm wrote ~2GB to the microSD card each day:
sudo dumpe2fs -h /dev/mmcblk0p2 | grep Lifetime >>disk_life.log
This initially appeared concerning as the card had an unused capacity of ~60GB (about 25 "full disk writes"). Knowing that SD cards are thought to be unreliable, and using a "worst case" calculation of 100 read/write cycles, gave a possible lifetime of 2500GB or <3 years. I considered using tmpfs to reduce this until, I found genuine 64GB High Endurance 64GB microSD cards at $10. This has a manufacturer's "Endurance" of up to 5,000 hours of FHD recording or >50TB or very approximately 60 years (pessimists divide by 10!) - So I'm pretty happy it will last as long as the 2TB SSD that I'm recording to. After trying it for a few days the actual speed of the system was about the same as the "fast" "official" RPi microSD card.
Starting "from scratch" to a fully working system; including installing the Pi in the FLIRC, formatting the OS on the microSD card, booting up, updating and installing all the software, editing cron etc., and adding auto-backup; took less than an hour. Replacing everything from backup would take less than 15 minutes.
Conclusion:
For me, the 2GB RPi-5 with FLIRC case, SSD and microSD works well. I now use it instead of the iMac. I already had some of the kit and was able to repurpose it for my use - It cost me AU$92 to set up, compared to AU$265 for the N95. The current uptime is 22 days with automatic weekly cron updates. Based on experience, I suspect that rebooting every couple of months or so will be adequate. As far as I can see - Unless Channels DVR has a major update (Please don't it works well as it is!) - This equipment will "see me out".