Serviio

Just a general interest question.

I see many posts saying a tv does not like transcoding.
Since the transcoding is done in the server with the usual intent of changing to a basic MPEG stream that looks like a normal MPEG file, how does the tv detect that the file has been transcoded. Or to put another way why can't the server transcode in such a way that it looks like it sending a normal mpeg file. The transcoded stf file certainly appears to be a normal mpeg file to me.

That is an excellent question, which I have no answer for. I know with my Samsung (Tizen OS) I can transmux files without issue, but when I try to play a transcoded file (WTV is all I have that needs it) it reports an unplayable file. Zip hasn't been able to determine what the issue is.

Yes it is an normal mpeg file... eventually.

zip's probably best to answer, but my limited understanding (based on observations rather than any true knowledge) is that the problems stems from transcoding on the fly. When streaming starts, the transcoding is not yet fully finished. So not all of the information about the final transcoded (mpeg) media file is necessarily available when the renderer needs it.

For example at the beginning of the transcode the file size and average bit rate won't be known (transcoding from say h.264 to mpeg2video will result in a much bigger file than the original) and this then impacts some devices that need this information. I believe Serviio tries to deal with this by sending a fake file size for some renderers?? (this is just based on comments zip has made, which I may have misinterpreted). How this is dealt with depends on the renderer. My PS4 for example shows no duration for any transcoded file - hence it's treated as a live stream by the renderer with no forwarding, rewinding or pausing. My Panasonic TV copes generally well, but some transcoded video's are cut short slightly. I think it also gets more complex as some devices seek by byte range while others seek by timecode and that impacts their ability to seek in transcoded files.

But it's a good question... I suspect the answer is far more complex than my limited understanding.

Mostly the fact the file length is not known.

So if you told the tv it will be longer than it really is, how would it know at the beginning, and I would expect it to be able to handle the shorter termination in the event of network failure or user premature quit at the end.

That's what Serviio does in some cases. Some TVs tend to ignore the specs though and (for example) send byte range requests even though Serviio says No.