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Thread: New R2 subtitle support - Error On conversion

  1. #1

    New R2 subtitle support - Error On conversion

    I recently upgraded to the R2 version of the Video Converter, for among other things it's support for retaining subtitles during conversion.

    I'm attempting to do a conversion using the Encoding MP4 (Nvidia HVEC H265), Audio Stream: Copy 1:1. No advanced settings, no dsp effects. Just looking to do the simplest conversion. I was trying to keep the test as stock / simple as possible.

    It almost immediately fails with the message: "Subtitle encoding currently only possible from text to text or bitmap to bitmap"

    I enabled Debug logging and it shows this:

    [7/8/2021 18:34:45] "C:\Program Files\dBpowerampVideo\ffmpeg-gpl.exe" -i "D:\Folder\Video.mkv" -map s -threads 4 -qp 24 -acodec copy -c:s mov_text -f mp4 -c:v hevc_nvenc -preset medium -y -ignore_unknown -hide_banner -progress "C:\Users\User\AppData\Local\Temp\_dbBFE3.tmp" -loglevel 16 "D:\Folder\Video- x265.tmp.mp4"
    [7/8/2021 18:34:45] Encoding loop...
    [7/8/2021 18:34:46] Encoding loop exit
    [7/8/2021 18:34:46] Subtitle encoding currently only possible from text to text or bitmap to bitmap
    [7/8/2021 18:34:46] Encoding exit

    A little searching on the web makes me think this has to do with the source being .mkv and the destination being .mp4. But I'm far from well versed in ffmpeg.

    I tried the same file using the Matroska (HVEC H265) for encoding and it seems like it may work. I don't care whether it's mp4 or mkv, but I'd like to use my video card for the conversion and there doesn't appear to be an encoding profile for Matroska (Nvidia HVEC H265).

    I'm guessing there are a few ways the software should handle things and a combination of feature request and bug report for the new release. Hoping to spark a fix.

    Thanks

  2. #2

    Re: New R2 subtitle support - Error On conversion

    I did some troubleshooting and believe I've confirmed what my initial web searches had indicated might be the case.

    It would appear that because the source file is a .mkv with the subtitle stream in pgs format there isn't a direct copy or conversion capability to mp4 container.

    I was able to use the custom Encoder type to play with the commands used in the MP4 (Nvidia HVEC H265) and the Matroska (HVEC H265) profiles.

    For subtitle copy support the MP4 encoder adds a -c:s mov_text command and the Matroska profile doesn't seem to currently do anything with / support subtitle stream.

    So I created a custom Encoder entry merging the values from these two and a ffmpeg doc referencing the copy command for -c:s. Resulting in
    Code:
    -threads 4 -qp 24 -acodec copy -c:s copy -f matroska -c:v hevc_nvenc -preset medium -y -ignore_unknown -hide_banner
    This seems to correctly create a mkv with a copy of the subtitle stream from the original and uses the nvidia encoder to re-encode the video stream.


    So questions/ requests.

    Is there a reason there isn't a Matroska (Nvidia HEVC H265) that includes the -c:s copy command? Is it easy enough to feature request the addition?

    Shouldn't the treatment of subtitle streams be a configurable item in the encoder profile settings like how audio options are handled?

    For the conversion error when pgs subtitles are found, I would think ideally the error would be caught and a recommendation made when converting a mkv to mp4 (especially since the canned profiles can't currently have their subtitle options changed). For example if I don't care about the subtitles in the source mkv, seems like I should be able to select and option to ignore the subtitle stream when re-encoding and saving to a mp4 container. Rather than have it just error.

    The internet would also make it seem like there are ways to either export for side car use and or convert subtitle stream types to different compatible versions for the different container types. So perhaps longer term feature request would be to support these subtitle conversions within the app as part of the convert process?

  3. #3

    Re: New R2 subtitle support - Error On conversion

    I have come across this problem with the source being a MKV ripped using MakeMKV from a bluray. Just adding my voice to just say I have come across this in the hopes it could be fixed some day.

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