[HELP] after encoding ass into mp4, but there is no subtitle at all

[Selur]

I found a way to reproduce the issue.
Will try look at it during the week, but not sure if I find the time.

Cu Selur

[ssdde]

yeah, I'm not wrong, there must be something wrong.

[Selur]

Question is what.
Unlike what you wrote remuxing the file without chapters does not fix the problem here.

-> Does it make a difference for you if you disable 'x264->Main->Automatically->Create qp file chapters' ?

[Selur]

Okay, remuxing to mkv does resolve the problem.
So the video stream itself is okay, the chapter times are okay.
And it's likely a bug in MP4Box, will have to do more testing to be sure.

Cu Selur

[ssdde]

-> Does it make a difference for you if you disable 'x264->Main->Automatically->Create qp file chapters' ?

under x264 - base, there is no Automatically. And i found x264 - Misc - Main - Automatically, there is a "Create qp file chapters", it's checked by default.


remuxing to mkv does resolve the problem?

no, it's impossible, after remuxing, it's still the same.

[Selur]

Sorry, meant:
'x264->Misc->Main->Automatically->Create qp file chapters'

Opening the laggy file in Hybrid, setting audio&video to passthrough all and saving the file as a .mkv file does fix the issue here.

Cu Selur

[ssdde]

good news! after uncheck "Create qp file chapters", then encode, everything is OK now. So what's "Create qp file chapters" is use for?

[Selur]

okay, no clue why that helps.

Try also keeping 'Create qp file chapters' enabled while making sure that 'x264->Frames->Advanced Frame Settings->Open GOP' is disabled.

So what's "Create qp file chapters" is use for?

It makes sure that at each chapter point an I frame is created to make sure that jumping to the chapter point properly works.

Cu Selur

Ps.: Using ffmpeg instead of MP4Box for muxing also works.

[ssdde]

this option can't check, it's always unenabled state no matter 'Create qp file chapters' checked or not.

[Selur]

Ah okay, it's a side effect of the 'ultrafast' preset, to be precise it can't be used when b-frames aren't used.