InterviewDB Question · USA

Audio Stream - Process and Buffer a Real-Time Audio Data Stream

phone

Question Details

Round 1 Coding

Problem

You are building an audio processing pipeline. Audio arrives as a continuous stream of integer samples. Implement an AudioBuffer that:
1. Accepts incoming samples one at a time.
2. When the internal buffer reaches a fixed frame_size, processes the frame (apply a simple gain factor) and emits it.
3. Allows querying how many complete frames have been emitted.

python
class AudioBuffer:
    def __init__(self, frame_size: int, gain: float):
        pass

    def write(self,

**sample**: int) -> list[int] | None:

**Returns** the processed frame when buffer is full; None otherwise
        pass

    def frames_emitted(self) -> int:
        pass

    def flush(self) -> list[int] | None:
        # Emit a partial frame padded with zeros if any samples remain
        pass

Example

buf = AudioBuffer(frame_size=4, gain=2.0)
buf.write(10)   # -> None
buf.write(20)   # -> None
buf.write(30)   # -> None
buf.write(40)   # -> [20, 40, 60, 80]  (gain applied)
buf.frames_emitted()  # -> 1
buf.write(50)
buf.flush()     # -> [100, 0, 0, 0]

Follow-ups

How do you handle overflow when gain causes sample values to exceed int16 range?
How would you implement a sliding window (overlapping frames) instead of non-overlapping?
If samples arrive from multiple concurrent threads, how do you make write thread-safe?
How do you design this for a real-time system where dropped frames cause audible glitches?

Full Details

Round 1 Coding

Problem

python
class AudioBuffer:
    def __init__(self, frame_size: int, gain: float):
        pass

    def write(self,

**sample**: int) -> list[int] | None:

**Returns** the processed frame when buffer is full; None otherwise
        pass

    def frames_emitted(self) -> int:
        pass

    def flush(self) -> list[int] | None:
        # Emit a partial frame padded with zeros if any samples remain
        pass

Example

buf = AudioBuffer(frame_size=4, gain=2.0)
buf.write(10)   # -> None
buf.write(20)   # -> None
buf.write(30)   # -> None
buf.write(40)   # -> [20, 40, 60, 80]  (gain applied)
buf.frames_emitted()  # -> 1
buf.write(50)
buf.flush()     # -> [100, 0, 0, 0]

Follow-ups

How do you handle overflow when gain causes sample values to exceed int16 range?
How would you implement a sliding window (overlapping frames) instead of non-overlapping?
If samples arrive from multiple concurrent threads, how do you make write thread-safe?
How do you design this for a real-time system where dropped frames cause audible glitches?

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About This Question

This is a reported interview question from a toma interview during the phone round.

It covers the following topics: Coding, Phone, Sliding Window .

Topics

Coding Phone Sliding Window

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Solve similar problems on LeetCode under timed conditions (25-35 minutes per medium difficulty). The goal is pattern recognition: recognize the underlying technique (sliding window, two-pointer, BFS, memoized recursion, etc.) within 60-90 seconds of reading. Strong candidates verbalize their hypothesis out loud before coding, then iterate based on feedback. Weak candidates dive into implementation immediately, lose time on the wrong approach, and run out of time for follow-ups.

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