Can my Synology NAS transcode 4K videos for my device?

Video transcoding refers to the process of converting video files originally unsupported by a media player into a compatible format and resolution. Different Synology NAS models are equipped with different transcoding capabilities. You can stream your video collection on your Synology NAS to a media player using Video Station, DS video or Media Server. Below are tables indicating the behavior of Synology NAS in respective scenarios.

Video Station and DS video

Table 1 shows the video transcoding capabilities of different Synology NAS groups when streaming video to popular media players with Video Station or DS video.


4K Group 1 4K Group 2
Win PC and Mac browsers * MP4, MOV and M4V: stream original video file
* MP4 (multi audio tracks) or MKV: remux video1
* Transcode video up to 1080p2
* Use 3rd party plugin for unsupported formats
* Transcode video up to 1080p3
* Use 3rd party plugin for unsupported formats
Apple TV * MP4: stream original video (without subtitles)
* MP4 and MKV: remux video (with subtitles)
* Transcode video up to 1080p
DLNA devices Transmit original files to the DLNA devices; supported formats depend on the device.
Chromecast * MP4, MOV, M4V, and MKV: stream original video (video codec: H.264 HP@L4.1; audio codec: AAC/MP3)
* MP4, MOV, M4V, and MKV: remux video if audio codec is AC3, or stream original video by enabling AC3 passthrough in DS video
* Transcode H.264/H.265 4K video to 1080p max * Transcode H.265 4K video to 1080p max
iOS * MP4:
iPhone 6s & later devices: stream original video
Older devices: stream original video in 1080p or lower; transcode 4K video up to 1080p
* MKV:
iPhone 6s & later devices: remux video
Older devices: remux video in 1080p or lower; transcode 4K video up to 1080p
Android * Supported formats depend on the device. We recommend installing MX Player for optimal experience.
* Transcode H.264/H.265 4K video to 1080p max * Transcode H.265 4K video to 1080p max
Windows Phone * MP4, WMV: stream original video
* Transcode video up to 720p
Roku players * MP4 (mpeg4 Pt 14), M4V, and MOV (video codec: h264 / mpeg4; audio codec: aac / ac3 / mp3 / none and non-5.1 aac): stream original video
* MKV: remux video
* Transcode video up to 1080p (resolution conditioned by Roku models)
Samsung Smart TV * Transcode video up to 1080p

Media Server

Table 2 shows the behavior of Synology NAS running Media Server.

4K Group 1 4K Group 2
DLNA devices * For XBOX 360, transcode video to ASF up to 480p
* For other DLNA devices, transcode video to TS up to 1080p
* Transcode video to TS up to 1080p
* XBOX 360 is not supported

Synology NAS Models and Groups

You can refer to the table below to determine which 4K video transcoding group your Synology NAS belongs to.

Supported Video Transcoding Type Applicable Models
4K Group 1 DS916+, DS716+, DS716+II, DS416play, DS216+, DS216+II
4K Group 2 DS216play
Note:
  1. Remuxing here refers to the process of transcoding the audio codec of your video while keeping the video codec intact. This enables your PC browser (without plugin) or your Apple TV to play MP4 or MKV videos whose audio codec is not supported.
  2. Any container or file extension in 4K 2160p (4096 x 2160 or 3840 x 2160) with codecs H.265 (HEVC) and H.264 (AVC), and in 1080p with codecs H.265 (HEVC), H.264 (AVC), MPEG-2 and VC-1 can be transcoded up to 1080p by Synology NAS in 4K Group 1. The maximum supported frame rate per second (FPS) is 30. These containers can be MKV, MP4, AVI, TS, MPG, WMV and more. However, these containers/file extensions might come in codecs other than the four mentioned. In that case, videos cannot be transcoded to 1080p. Please refer to this article for more information on the container formats.
  3. Any container or file extension in 4K 2160p (3840 x 2160) with codecs H.265 (HEVC), and in 1080p with codecs H.265 (HEVC), H.264 (AVC), MPEG-4 Part 2 (XVID, DIVX5), MPEG-2, and VC-1 can be transcoded up to 1080p by Synology NAS in 4K Group 2. The maximum supported frame rate per second (FPS) is 30. These containers can be MKV, MP4, AVI, TS, MPG, WMV and more. However, these containers/file extensions might come in codecs other than the four mentioned. In that case, videos cannot be transcoded to 1080p. At this time, 4K Group 2 does not support transcoding any container or file extension in 4K 2160p (3840 x 2160) with codecs H.264 (AVC). Please refer to this article for more information on the container formats. Other codecs are not supported.
  4. 4K Group 1 is capable of transcoding 3GP, 3G2, ASF, AVI, DAT, DivX, DVR-MS, FLV, M2T, M2TS, M4V, MKV, MP4, MTS, MOV, QT, TP, TRP, TS, VOB, WMV, XviD, and RMVB up to 720p. For the complete list of supported file formats in the original and transcoded streams, please see the specifications of Video Station and DS video.
  5. 4K Group 2 supports codecs listed in Note 3. Other codecs are not supported.
  6. For online transcoding, Hi10 profile is not supported in H.264, and Main 10 profile is not supported in HEVC (H.265).
  7. For formats supported by Synology NAS devices without 4K video transcoding capability, please refer to this article for more information.
  8. 4K transcoding is not supported on third-party software applications.
  9. Video transcoding for HD DTV live streaming is not supported.