converting MKV to MP4 for use on Plex server

[Troy_Piggins]

Plex server doesn't seem to recognise MKV files, so I'm trying to convert them to MP4 files that I know work. Plex website recommends MP4, H.264, 30fps, 8bit, AAC for max compatibility I think. I've been searching around and see some recommendations to use something like
avconv -i input_file.mkv -codec copy output.mp4, but when I try this I get errors:

...
[mp4 @ 0x1daf3a0] track 0: could not find tag, codec not currently supported in container
...
Could not write header for output file #0 (incorrect codec parameters ?)

So I tried
avconv -i input_file.mkv -c:v libx264 -c:a aac output.mp4 but get:

...
[buffer @ 0x2273d60] Invalid pixel format string '-1'
Error opening filters!


Any tips? All of this containers/codecs stuff is way over my head.

[Yellow Pasque]

So what kind of video/audio is actually in your mkv?

sudo apt-get install mediainfo
mediainfo input_file.mkv

Plex supposedly will transcode unsupported formats itself. https://support.plex.tv/hc/en-us/articles/203810286-What-media-formats-are-supported-

[Troy_Piggins]

$ mediainfo input_file.mkv


GeneralUnique ID : 211214885490128882012812617229213536485 (0x9EE681DC38EA67D59A54DDF5319290E5)
Complete name : input_file.mkv
Format : Matroska
Format version : Version 2
File size : 250 MiB
Duration : 51mn 54s
Overall bit rate : 673 Kbps
Encoded date : UTC 2015-11-23 14:11:37
Writing application : mkvmerge v4.0.0 ('The Stars were mine') built on Jun 5 2010 17:44:09
Writing library : libebml v1.0.0 + libmatroska v1.0.0
DURATION : 00:51:51.765000000
NUMBER_OF_FRAMES : 72932
NUMBER_OF_BYTES : 24889056
_STATISTICS_WRITING_APP : mkvmerge v7.8.0 ('River Man') 32bit built on Mar 27 2015 16:18:02
_STATISTICS_WRITING_DATE_UTC : 2015-11-22 12:52:38
_STATISTICS_TAGS : BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES


Video
ID : 1
Format : V_MPEGH/ISO/HEVC
Codec ID : V_MPEGH/ISO/HEVC
Duration : 51mn 54s
Width : 1 280 pixels
Height : 720 pixels
Display aspect ratio : 16:9
Frame rate : 23.976 fps
Default : No
Forced : No


Audio
ID : 2
Format : AAC
Format/Info : Advanced Audio Codec
Format profile : HE-AAC / LC
Codec ID : A_AAC
Duration : 51mn 54s
Channel(s) : 2 channels
Channel positions : Front: L R
Sampling rate : 48.0 KHz / 24.0 KHz
Compression mode : Lossy
Default : No
Forced : No


Text
ID : 3
Format : UTF-8
Codec ID : S_TEXT/UTF8
Codec ID/Info : UTF-8 Plain Text
Default : Yes
Forced : No

[FakeOutdoorsman]

HEVC / H.265 can go in to MP4 container, but:


I don't know anything about Plex or if it supports HEVC.
avconv is buggy.


If Plex does support it then get a recent version of the real ffmpeg (http://johnvansickle.com/ffmpeg/) then just re-mux:

ffmpeg -i input.mkv -c copy output.mp4

If not, then get ffmpeg and then re-encode the video and stream copy the audio:

ffmpeg -i input.mkv -c:v libx264 -c:a copy output.mp4

If you want to test instead of encoding the whole video just add "-t 60" for a 60 second output file duration.

[andrew.46]

It is very much a side issue Troy but I see that your hevc video stream was muxed with mkvmerge 4.0.0:



Encoded date : UTC 2015-11-23 14:11:37
Writing application : mkvmerge v4.0.0 ('The Stars were mine') built on Jun 5 2010 17:44:09
Writing library : libebml v1.0.0 + libmatroska v1.0.0


which is a little odd as mkvmerge did not really get proper hevc support until v6.8.0:



* Released v6.8.0.

2014-02-28 Moritz Bunkus <moritz@bunkus.org>

* mkvmerge, mkvextract: new feature: added support for h.265/HEVC
by merging the patches from DivX/Rovi Corp. So far HEVC is only
supported as elementary streams and read from other Matroska
files.


and I puzzle over the next couple of lines:



_STATISTICS_WRITING_APP : mkvmerge v7.8.0 ('River Man') 32bit built on Mar 27 2015 16:18:02


Changelog details here (https://mkvtoolnix.download/doc/ChangeLog). Probably has no bearing on your issue though...

[Yellow Pasque]

I don't know anything about Plex or if it supports HEVC.

Plex's changelog indicates it gained support for HEVC in version 0.9.10.0.

So what version of Plex do you have?