Why Do Some Channel Changes Take More Time?

TABLE OF CONTENTS

• Quick Answer
• Technical Answer (Long Answer)
  • 1. Changing Channels Within the Same Frequency – Fastest Process
  • 2. Changing Channels on Different Frequencies (Same Standard) – Requires Retuning
  • 3. Switching Between ATSC 1.0 and ATSC 3.0 – Most Processing Required
• How ADTH Tuners Are Optimized for Efficient Switching

Quick Answer

The time required to change channels depends on the number of steps the tuner must take. Channels that share the same frequency switch almost instantly because no retuning is required. When switching between frequencies, the tuner must lock onto a new signal, which takes additional processing.

The most complex transitions occur when switching between ATSC 1.0 and ATSC 3.0, as these are fundamentally different broadcast standards. The tuner’s Software-Defined Radio (SDR) demodulator must fully reset and switch between two different modulation schemes, transport formats, and decoding pipelines.

ADTH tuners are designed for fast and efficient channel changes, ensuring optimal performance while maintaining high-quality reception.

How Different Channel Changes Are Processed

Technical Answer (Long Answer)

1. Changing Channels Within the Same Frequency – Fastest Process

Some channels are transmitted together on the same RF frequency as a multiplexed signal. In this case:

• The tuner remains locked on the same RF signal (no retuning required).
• The modulation and transport stream remain unchanged.
• The decoder simply switches streams within the same multiplex.

This is the most efficient type of channel change because the tuner does not need to reconfigure any hardware settings or reacquire a signal.

Technical Process:

1. The tuner identifies the new stream in the already-received multiplex.
2. It signals the decoder to switch streams, requiring only a few milliseconds.
3. The video and audio buffers reload with the new program data.

Since no RF adjustments or demodulation changes are needed, this process is near-instantaneous.

2. Changing Channels on Different Frequencies (Same Standard) – Requires Retuning

When switching between ATSC 1.0 channels on different frequencies, or between ATSC 3.0 channels on different frequencies, the tuner must:

1. Adjust RF front-end tuning to the new frequency.
2. Acquire and synchronize with the new signal, detecting modulation parameters.
3. Reinitialize the demodulator to extract the transport stream.
4. Flush and reload video and audio buffers.

RF Tuning & Signal Lock

• ATSC 1.0 and ATSC 3.0 use different channel bandwidths (ATSC 1.0 = 6 MHz, ATSC 3.0 can vary).
• The AGC (Automatic Gain Control) must stabilize before the demodulator locks onto the new signal.
• Once locked, the PLP (Physical Layer Pipe) or MPEG-2 TS is extracted, allowing the tuner to decode the new program.

This process takes longer than switching within the same frequency because the tuner must retune, reacquire, and resynchronize with the new RF signal before playback begins.

3. Switching Between ATSC 1.0 and ATSC 3.0 – Most Processing Required

ATSC 1.0 and ATSC 3.0 use fundamentally different transmission technologies, so the tuner cannot simply retune—it must reconfigure itself entirely.

Key Differences That Require Full Demodulator Reset

Because ATSC 1.0 and ATSC 3.0 use completely different encoding, error correction, and transmission methods, switching between them requires the SDR demodulator to reset and switch modes.

Step-by-Step Process When Switching Between ATSC 1.0 & 3.0

1. Reset the Demodulator: The tuner shuts down its current signal processing chain.
2. Switch RF Mode: The front-end adjusts its gain settings to accommodate a different modulation type (8VSB vs. OFDM).
3. Reinitialize Demodulation: The SDR demodulator reloads firmware to support either ATSC 1.0 or ATSC 3.0.
4. Reacquire Signal Lock: The tuner searches for pilot signals and synchronizes with the correct broadcast standard.
5. Restart Decoder Pipeline: Since ATSC 3.0 uses HEVC and IP-based transport, the entire decoding structure must be switched.
6. Buffer Reload & Playback Start: The video and audio buffers are refreshed with the new format before playback begins.

Why This Takes More Steps Than Any Other Channel Change

• The modulation scheme must be completely switched.
• The transport stream type changes from MPEG-2 TS to IP-based.
• The video and audio decoding pipeline must be reconfigured.
• ATSC 3.0 stations may also have internet-based content, requiring the tuner to check for additional network features.

Since this involves both hardware-level reconfiguration and software-level processing changes, it requires the most steps of any channel transition.

How ADTH Tuners Are Optimized for Efficient Switching

While certain channel changes require more steps due to the nature of digital broadcasting, ADTH tuners are designed to optimize each transition by:

• Fast signal acquisition algorithms to minimize retuning time.
• Efficient SDR switching to quickly handle ATSC 1.0 ↔ ATSC 3.0 transitions.
• Optimized decoding pipelines to rapidly switch between transport formats.

Whether you're switching within the same frequency, across different channels, or between ATSC 1.0 and ATSC 3.0, ADTH tuners ensure the fastest, most reliable experience possible while maintaining excellent signal quality.

If you have any questions, our support team is always available to help!