Synology NAS / How to play DTS and AC3 videos with Video Station

If a video with DTS or AC3 audio has no sound in Video Station, first check the DSM version and the file’s actual audio codec. Where Video Station is available, first consider playing the original file in an external player or converting its audio to a supported format. Video Station is no longer officially available starting with DSM 7.2.2, so those systems require a different playback approach rather than just an additional codec.

In the past, installing FFmpeg from SynoCommunity was presented as a solution, but package installation and integration with Video Station are separate. This article explains the currently applicable methods and distinguishes what to check in older environments.

The solution varies depending on the DSM version

DSM (DiskStation Manager) is the operating system of Synology NAS. NAS (Network Attached Storage) is a device for storing and sharing files over a network. After logging into DSM, check the current version at [Control Panel → Update & Restore → DSM Update]. You can also check it at [Control Panel → Info Center → General]. The menu path is based on Guidance for Checking Synology's DSM Version.

DSM official release notes state that Video Station cannot be used on DSM 7.2.2. Interpreting the missing installation menu as a DTS codec issue changes the direction of the solution. Before upgrading DSM, check the changes in the packages you use and DSM configuration backup method. Prepare configuration backup and original video backup separately.

Distinguish DTS, AC3 and EAC3

A codec is a method for compressing and then playing back video or audio. DTS (Digital Theater Systems audio), AC3 (Audio Coding 3, Dolby Digital), and EAC3 (Enhanced AC-3, Dolby Digital Plus) are different audio formats. Even if a file's name says AC3, the actual track could be EAC3, or there could be multiple audio tracks within one file.

Synology's Video Station DTS and EAC3 Playback Issue Guide explains the support limitations for DTS audio and certain Dolby formats like EAC3 and TrueHD. Therefore, you should not assume that AC3 and EAC3 are treated as the same format, or that all AC3 files cannot be played.

1. Copy the problematic video to your PC and open it with VLC media player.
2. In VLC for Windows, open [Tools → Codec Information] to check the video and audio codec. This menu is explained in VLC Official Codec Check Guide.
3. If there are multiple audio tracks, try selecting different tracks in VLC under [Audio → Audio Track]. Note which track produces sound.
4. Check whether the same file plays properly on a PC. If it plays on a PC but fails on Video Station or TV, first check the supported formats of the playback path.

MKV and MP4 are container formats that hold video, audio, and subtitles. Even if the extensions are the same, the internal codecs may differ, so do not determine playback capability based only on the extension.

Play the original NAS file in an external player

A method you can try first without converting the file is to open the NAS video directly with a player like VLC. Since the NAS delivers the file and the playback device processes the codec, the device and player you use must support the video and audio.

When a Windows PC and NAS are on the same local network, you can use SMB (Server Message Block, a network file sharing method).

1. Check in DSM under [Control Panel → File Services → SMB] that the SMB service is enabled.
2. Enter the path in the address bar of Windows File Explorer in the following format. Replace NAS_ADDRESS and SHARE_NAME with the actual NAS IP address or name and the video folder name.

\\NAS_ADDRESS\SHARE_NAME

3. Log in with a NAS account that has read permissions on the shared folder. First, check if the file list is visible.
4. In VLC's [Media → Open File], select the video, or drag and drop the file from Explorer into the VLC window.
5. Check if the audio and subtitles are working correctly. If buffering occurs, copy the same file to the PC and play it again to distinguish between network issues and playback performance problems.

For enabling SMB and device-specific playback methods, refer to Synology NAS Video Streaming Guide, and for opening files, refer to VLC Official File Playback Guide. This procedure assumes a local network. On smartphones, check the network sharing connection feature provided by the app, and do not assume that menus and codec support are the same across devices.

If you want to manage video lists and playback history together after DSM 7.2.2, you can also consider a separate media server. Synology provides Plex Media Server Installation and Migration Guide. Not all codecs will play simply by installing, so check the supported formats of the device you plan to use and the conversion conditions of the server.

Keep the video and convert only the audio

If it is difficult to change the TV or playback app, and sound does not come out only from certain files, audio conversion is an alternative. First, keep the original, and choose an audio format supported by the actual playback device.

The example below shows converting the audio of an MKV file to AAC (Advanced Audio Coding) stereo using a video and audio processing tool called FFmpeg on a PC. This is an example for a device that can play AAC directly. Synology explains that from DSM 7.1.1, server-side transcoding of AAC audio is not supported, so simply converting to AAC does not resolve all Video Station environments. The applicable conditions can be checked at AAC playback limitation guide.

1. Check the link for the executable file suitable for your operating system on FFmpeg official download page. On Windows, extract the downloaded build and check the folder that contains ffmpeg.exe.
2. On Windows, right-click on an empty space in that folder and select [Open in Terminal]. If the installation path is already registered in PATH, it can be executed from other folders as well.
3. Copy the MKV file to be converted into the working folder. Replace input.mkv in the following command with the actual original file name. Specify a name for the output file that is different from the original.

ffmpeg -n -i "input.mkv" -map 0 -c copy -c:a aac -ac 2 -b:a 192k "output-aac.mkv"

If you run it in Windows PowerShell without setting the PATH, from the folder of the executable, replace ffmpeg at the beginning of the command with .\ffmpeg.exe.

• -n: Will not overwrite if there is an output file with the same name.
• -map 0: Selects all streams from the original for the output.
• -c copy: By default, copies the streams as-is. The following -c:a aac applies only to audio, converting all audio tracks to AAC.
• -ac 2 -b:a 192k: Sets audio to 2 channels, 192 kbit/s. This value is for this example's settings and is not a setting that preserves multichannel spatiality.

The video is not recompressed, so video quality is maintained, but the audio is converted using lossy compression. Other streams such as subtitles are copied, and the example assumes MKV input and MKV output. If you change to a different container, you need to separately check the compatibility of the included streams. The meaning of the options is based on the official FFmpeg command documentation.

4. Once the conversion is complete, check the output file's length, sound, subtitles, and the synchronization of audio and video on your PC.
5. Copy the output file to the NAS with a name distinct from the original, and then play it again on the TV or app where it will actually be used.
6. If it fails, delete the output file and revert to the archived original. If the device does not support AAC, it must be converted to another format specified in the device's manual.

Check SynoCommunity FFmpeg integration in older environments

SynoCommunity is a project that provides community packages for Synology NAS. If you are considering FFmpeg in an older environment that still uses Video Station, you should first check whether NAS model, DSM version, Video Station version, and FFmpeg package version are compatible. You can check the current package composition and supported targets at SynoCommunity package list.

The basic procedure for registering the package repository is as follows. This is a procedure that guides the FFmpeg installation path and does not complete the Video Station codec integration procedure.

1. In DSM, open [Package Center → Settings → Package Sources].
2. Click [Add], enter SynoCommunity as the name, and enter the following HTTPS address as the location.

https://packages.synocommunity.com/

3. After saving the settings, find the FFmpeg package in the [Community] section of the Package Center. If the trust level needs to be set in DSM 6.x, set the trust level in [Settings → General] to [Synology Inc. and trusted publishers]. For differences by version, check SynoCommunity official installation guide.
4. Check the compatibility conditions and descriptions of packages that can be installed on the NAS. If multiple FFmpeg versions are shown, do not arbitrarily choose one; verify the version required by the tool you intend to use.
5. If the compatibility conditions are met, click [Install] for the package and complete the installation. In DSM 7.x, a notification may appear indicating that it is a third-party package not verified by Synology. Even after the installation is complete, you need to separately check whether Video Station integration works as explained below.

Some environments require separate integration adjustments. For example, the VideoStation-FFMPEG-Patcher project provides separate patches for DTS, EAC3, and TrueHD conversion. This is not an official Synology feature and is not the same as installing the FFmpeg package. The explanation in existing articles that "installing FFmpeg immediately enables DTS playback" does not apply to all versions.

Changing formats while playing on a NAS is called transcoding. The load of this process varies depending on whether video conversion occurs, the file format, NAS performance, and the number of simultaneous plays. Check CPU usage in DSM's Resource Monitor during playback and if the load or stuttering is high, either convert the file in advance on a PC or let the device play the original directly. Before removing an installed package, also check whether other packages are using that FFmpeg.

Troubleshooting checklist

1. Check file access: If the shared folder does not open, first check the NAS address, account permissions, and network connection rather than the codec.
2. Check local playback of the original: If the file copied to the PC also fails, check for file corruption or issues with the player’s compatibility.
3. Check the audio track: Verify that you have selected the desired language track and check whether it is AC3 or EAC3.
4. Compare playback paths: Check the same file on the browser, external player, and TV to narrow down the path where it fails.
5. Check conversion results: If the converted file works on the PC but fails on the TV, also check the video codec, audio codec, and container that the TV supports. Changing only the audio track will not solve video codec issues.

If the NAS itself does not appear on the TV, the cause may differ from a problem where only the sound does not play. In that case, also refer to Things to check when the Synology Media Server does not connect to a smart TV.

Frequently Asked Questions

If I install FFmpeg on DSM 7.2.2, will Video Station appear again?

FFmpeg is a media processing tool and does not provide Video Station itself. Video Station is no longer officially available starting with DSM 7.2.2; use another player or media server on those systems.

If I change it to AAC, will sound come out on all devices?

No. The final playback device must support AAC directly, and the video codec and container must also be compatible. You also need to check the AAC server-side transcoding limitation since DSM 7.1.1.

If I convert only the audio with FFmpeg, will the quality of the original video drop?

If you copy the video stream as in the example in this article, the video is not recompressed. However, the audio is recompressed to AAC, and the 2-channel setting changes multi-channel sound to stereo. Keep the original file separately.