I’ve been recording some of the events for the Olympics, and noticed that 1.5 hours of recording is 10+GB.
Size 10.44 GB
Container MPEGTS
Codec H264
Bitrate 15582 kbps
Bit Depth 8
Chroma Location left
Chroma Subsampling 4:2:0
Closed Captions true
Coded Height 1088
Coded Width 1920
Frame Rate 29.97 fps
Height 1080
Level 4.0
Profile main
Ref Frames 4
Scan Type progressive
Stream Identifier 256
Width 1920
Display Title 1080p (H.264)
Extended Display Title 1080p (H.264)
On my Live TV settings, I have “Convert video while recording” set to “transcode”. It seems like there are a few things going on.
While recording, it is hitting my CPU pretty hard. I have HW transcoding enabled and an Arc A380 that seems to work when playing back other items, so I’m not sure why it’s not being used here
For being 10.44GB, the video quality doesn’t look particularly crisp. It seems like it’s doing a very fast CPU transcoding, despite my settings set to prefer higher quality transcodes.
It doesn’t look like Plex supports using HW to do transcodes of live TV while recording? Is the recommended way of dealing with this still setting up post-processing scripts? I’m surprised this isn’t more flexible. Maybe I’m missing something?
I don’t have one, but if the audio is being converted, it drives up CPU usage because it’s done in software not HW. Subtitles are another factor during playback, but I don’t know if this applies to what you are doing. Maybe someone else can speak to quality. At that bitrate I would hope for nearly perfect picture too.
If you have transccding set to a high preset quality setting the resulting stream is going to be larger. You’re taking a lossy source codec and transcoding to another lossy codec. The bitrate will need to be high as there is loss of quality from generational encoding and change in codec, too. This is why direct-play is always preferred when possible.
The transcode also deinterlaced your video. Storing whole frames versus a ½ height fields would affect size, as would changing the bitrate from 6k to 15k to preserve quality like nx6 mentioned. It looks like Plex also is using 4 CABAC Ref frames rather than the 1 used in the original.
Are you investigating external conversion to save space? Maybe you’re just curious what’s happening though.
I would probably suggest external conversion to HEVC. Probably transcode audio, too if it’s Dolby Digital in the source and a high bitrate. Maybe set it up to run during the night (Paris time ) so it doesn’t impact other use on the server.
It doesn’t look like the transcode changed it at all.
I don’t really want to put time into an external conversion to save space, as I’m mainly just watching the bits I want after the fact and am not worried about archiving them. I’m mostly just curious about why the live transcoding function even exists without any options if it just uses extra processing and increases the size of the recording. Maybe on the off chance you’d want to direct play later, to avoid transcoding in the future? Luckily most of my clients seem to support MPEG2VIDEO anyway.
) so it doesn’t impact other use on the server.