Quick answer: What retailers call an RCA adapter to HDMI is really a converter: an active box with an analogue to digital chip, a scaler and an audio embedder. Budget AU$35 to AU$70. It outputs 1080p60, embeds stereo as PCM at 48 kHz and adds 16 to 50 ms of latency. A passive plug with no power supply cannot produce HDMI, whatever the listing says. Check that the unit accepts 576i at 50 Hz, since a 60 Hz only box will not lock to Australian composite.
Two listings look identical and behave nothing alike. One is a 30 mm plug with no chip, which only rewires pins and cannot create a digital stream. The other is a small metal box with a 5 V input, which converts, scales and embeds audio. Buying the first by mistake is the most common reason an old DVD player still shows nothing.
Adapter or Converter: What the Box Contains
The passive plug and why it fails
Composite video is an analogue waveform at 1 V peak to peak. HDMI is three differential data pairs at multi gigabit rates. No arrangement of pins turns one into the other, so a plug sold as passive either contains a hidden chip or does nothing. If the listing shows no power input and no chip, it is the second kind.
What a real converter adds
A working unit contains an analogue front end with 75 ohm termination, a video decoder that separates sync, a scaler, and an HDMI transmitter. That is four active stages, which is why the box needs 5 V at 1 A and why it costs more than a cable.
Audio Embedding and Where It Goes Wrong
Stereo PCM is the ceiling
The red and white plugs carry stereo line audio, and the converter digitises it to 48 kHz PCM and inserts it into the HDMI stream. Two channel PCM is all HDMI needs for stereo, so this part is simple. Problems start when the source is set to a surround mode the converter cannot read, which produces silence rather than a downmix.
Some boxes take audio from a 3.5 mm jack instead of phono sockets,. Where the display has no speakers, the HDMI feed goes to an amplifier first, and the converter audio setting must stay on PCM rather than bitstream.
| Setup | Latency added (ms) | Audio path | Typical price (AUD) |
|---|
| Composite to HDMI, stereo | 16 to 30 | PCM 48 kHz, 2 ch | AU$35 to AU$50 |
| Component to HDMI, stereo | 20 to 35 | PCM 48 kHz, 2 ch | AU$45 to AU$70 |
| Composite to HDMI, 3.5 mm in | 16 to 30 | PCM 48 kHz, 2 ch | AU$30 to AU$45 |
| Composite with scaler to 4K | 35 to 50 | PCM 48 kHz, 2 ch | AU$55 to AU$70 |
| Dual output box | 20 to 40 | PCM 48 kHz, 2 ch | AU$60 to AU$70 |
Latency, Frame Rates and Sync
Every converter buffers at least one frame, and a deinterlacer needs two fields before it can output a frame. At 50 Hz that is 20 ms before scaling. Add television processing and the audio can arrive 60 ms early, which viewers notice as mouths moving ahead of voices on a close up.
Correcting lip sync
Fix it at the amplifier or television with a lip sync or audio delay setting in 10 ms steps. Do not chase the delay by splitting audio before the converter, because that removes the delay from the audio path and doubles the error.
Frame rate matters too. Australian composite sources run 576i at 50 Hz, and a converter set to 60 Hz output repeats frames unevenly, which shows as a small stutter every second. Choose a 50 Hz output mode when the menu offers one.
Testing Before a Permanent Install
Bench checklist
Power the converter from its own supply, feed a known good source, and confirm the display shows a stable image for 10 minutes. Then switch the source off and on three times and watch for the handshake to fail.
Once the chain works, split it deliberately. A powered hdmi splitter versus switch with EDID memory keeps the converter output stable when a second display is powered down, and a hdmi cable rating categories check tells you which lead suits 1080p60 over the planned distance. For recording, an hdmi to usb adapter captures the converted output at 1080p60 on a laptop.
Send the source list, socket types and display model to zongcarrie@zh-zong.com or call +86 13543026126 for a converter shortlist with latency figures, AUD pricing and freight to any Australian state.
Practical scenarios
- Situation: A Hobart church wants a DVD player and a laptop on one projector. What to do: Convert the DVD player once, then switch HDMI inputs rather than swapping analogue plugs.
- Situation: A Parramatta apartment has a turntable and a television with no analogue input. What to do: Use a phono preamp to line level, then a converter that embeds stereo as PCM.
- Situation: A Cairns resort replays a welcome video from an old media player. What to do: Set the player to 16:9 and 576i, convert to 1080p50, and lock the converter output.
- Situation: A Western Sydney warehouse records training sessions from a legacy camera. What to do: Convert to 1080p60 and capture through USB 3.0 rather than a television tuner card.
FAQ
Can a passive RCA adapter output HDMI?
No. Converting an analogue waveform into a digital HDMI stream requires powered circuitry, so any working product contains a chip and a supply. Plugs sold as passive either hide a chip in the shell or simply rewire pins and produce nothing on an HDMI display.
Why is the audio out of sync?
The converter delays video by at least one frame while audio passes through almost instantly, so sound arrives early. Apply an audio delay of 20 to 60 ms on the amplifier or television and adjust in small steps while a person speaks on screen until the timing looks natural.
Will it pass 1080p from a DVD player?
A DVD player outputs 576i or 576p, not 1080p, so the converter scales up rather than passing 1080p through. The output is 1080p60 or 1080p50 depending on the menu, and detail stays at DVD level. Only a Blu-ray player produces a native 1080p signal.
