Transcoding audio files and HDMI ARC versus HDMI eARC

General Discussions
1

I’d really appreciate hearing from someone who can explain HDMI ARC and HDMI eARC, particularly in the context of transcoding. My goal is to have a 2.1 home theater system that can play lossless audio files from movies (that is, Dolby TrueHD and DTS-HD MA). I was considering the Yamaha R-N2000A integrated amplifier, which has an ARC port rather than an eARC port. Then, I thought I should consider buying an all-analog integrated amplifier with balanced inputs. Along those lines, I purchased a music streamer that has both balanced outputs and an eARC port. From what I have found on the website of one merchant, the streamer supports 2-channel PCM and Dolby Digital audio (up to 24-bit/192kHz), but it is not compatible with DTS and other multichannel audio formats. On another website, I read that the streamer can down mix audio files. I connected the streamer via an HDMI cable to my 2017 model Sony TV, which has an ARC port.

Most of the time, I use an NVIDIA Shield TV Pro to watch movies stored on a NAS. When I stream a movie having TrueHD 7.1 audio, neither the audio nor the video file is processed as Direct Play. Instead, the audio signal is transcoded into something called TrueHD Opus. In contrast, when I stream a movie having DTS-HD MA 7.1 audio, both audio and video files are processed as Direct Play.

Questions:

  1. Is the transcoding of the Dolby TrueHD files occurring because of my TV’s ARC port or because of the streamer’s limited eARC port?

  2. Put differently, if my next TV has an eARC port that can decode both Dolby TrueHD and DTS-HD MA audio files, will the eARC port on the music streamer prevent it from playing a lossless soundtrack in 2-channel PCM?

  3. Still differently, when a TV decodes a Dolby TrueHD 7.1 audio file, will the TV output 2-channel PCM via an HDMI cable connected to another device, such as the music streamer? Thank you very much.

2

HDMI-ARC and eARC apply only when passing audio between a TV and audio equipment (amp, receiver, sound bar, etc.). Devices such as streaming boxes, DVD players, etc. do not need ARC/eARC capability.

For eARC, both ends must support it. Otherwise, it will fall back to ARC.

HDMI-ARC cannot pass lossless audio such as TrueHD or DTS-HD. It will pass AC3, EAC3, and DTS up to 5.1 channels and PCM 2.0.

Given your TV supports ARC, but not eARC, it will not pass TrueHD/DTS-HD back to any audio gear.

If you want TrueHD/DTS-HD audio:

Nvidia Shield Pro ← HDMI → Audio Equipment ← HDMI-ARC → TV

The audio gear will play TrueHD/DTS-HD/etc. audio and pass the video to the TV.

If your TV supports 4K HDR/Dolby Vision video, make sure the audio gear can pass those video formats. Some older receivers, etc. can pass 4K, but not 4K HDR/DV video.

The audio is transcoded to Opus. This is expected, as HDMI-ARC cannot pass TrueHD audio.

DTS-HD audio consists of two parts: (a) the lossy DTS 5.1 core; and (b) additional data forming the lossless portion.

The TV (not Plex) strips the “-HD MA” portion and passes the lossy DTS 5.1 core over HDMI-ARC.

This allows the stream to direct play instead of transcoding the audio.

FYI, TrueHD is a separate codec from AC3/EAC3. There is no “core” to pass like with DTS. That is why it is transcoded by Plex.

3

Hello.

Your explanation is much better than what I found online after repeated searches. Earlier today, I found a setting on my TV that I had set and forgotten about in 2017. That setting tells the TV to output PCM audio, which supposedly is lossless audio. My primary goal is to get lossless audio sent to a pair of loudspeakers.

Some people recommend connecting devices, such as blu ray players, to the TV itself rather than to an AVR because TVs are better at processing video signals. Of course, the TV generally would be connected to the eARC input of the AVR that is processing the audio signals. I would like my next TV, which will have eARC and be able process both TrueHD and DTS-HD MA, to output PCM audio to either: (1) the eARC input on a stereo music streamer, which eventually will be connected to an analog integrated amplifier (e.g., Yamaha A-S2200), or (2) the ARC input on a digital integrated amplifier (e.g., Yamaha R-N2000A). If I read your analysis correctly, I should be able to achieve this goal. If not, I will buy another AVR to replace my broken AVR.

Thanks for all your help.

4

The AVR does not process the video signal (unless you tell it to do so). It passes it through unmodified to the TV.

Which is better at downmixing audio, your audio equipment or the TV?

Configuring the TV for PCM tells it to downmix all audio to PCM 2.0.

Just as I would not want my AVR modifying video, I’m not sure I want my TV modifying my audio signals.

Listen with the TV configured for passthrough and PCM, but on the surface, it seems the AVR would be better at downmixing audio.

Writing strictly from a Plex point of view, I would choose neither the A-S2200 nor the R-N200A.

The reason is that neither have HDMI inputs or a HDMI-eARC output. This means something besides the amplifier (such as the TV, Shield, or Plex Media Server) will have to modify the audio signal first.

Note: Somebody probably makes a pre-amp with HDMI capability that could pass the video to the TV and downmix & pass audio to the amp. Fronting the amp with the pre-amp, would provide AVR-like capability. However, I’ve no idea where to look for such an item.

Consider purchasing an AVR with HDMI inputs and a HDMI-eARC output. This will let the AVR perform any audio downmixing, etc. Make sure it supports 4K HDR 60 Hz passthrough (HDMI 2.0b+).

Then connect the Shield to an HDMI input on the AVR and the TV to the HDMI-eARC port.

The AVR will do what it does best - handle the audio.

The TV will do what it does best - handle the video.

5

Hello.

In 2023, I bought a Marantz Cinema 70S as my first AVR and used it in the bedroom of my apartment until its headphone jack quit working. I planned to upgrade my system after moving into a house either by buying a more powerful AVR or by buying an external amplifier because most AVRs reportedly are not very good at powering 4 ohm speakers with low sensitivity. Because I was using the headphone jack, I set up the AVR as a 2-speaker system with the AVR’s video processing function disabled. For my purposes, the Yamaha A-S 2200 should be fine as an external amplifier because it has home theater bypass and reportedly is stable down to 4 ohms. My Cinema 70S still outputs power to loudspeakers, so its pre-outs should send audio signals to an external amplifier.

After considering your points about the Yamaha R-N2000A, I think that digital integrated amplifiers probably were designed for people who stream videos from Netflix, Amazon Prime, etc., using the apps on their TV. That does not interest me. So, I think my query has been resolved, and I again thank you for all of your help.

By the way, I no longer receive an email when you respond to my post. Is that feature gone?

6

This topic was automatically closed 90 days after the last reply. New replies are no longer allowed.