Adaptive Bitrate Content Delivery Simulator (2D)

Mobile Network

Network class

Volatility (handoffs, congestion) 50%

ABR Algorithm

Safety margin 0.90×

Live Readouts (Adaptive)

Throughput now

0.0 Mbps

Buffer

0.0 s

Current tier

–

Rebuffer events

Avg. bitrate played

0.0 Mbps

Quality switches

Naive Baseline (Always Max)

Rebuffer events

Rebuffer time

0.0 s

How it works

Rich mobile content (video, high‑res images, embedded media) is delivered in short chunks, each independently encodable at several quality tiers — a "bitrate ladder". A client‑side ABR (adaptive bitrate) algorithm decides, chunk by chunk, which tier to fetch next.

1. Measure throughput of each finished chunk:
     T_i = chunkSizeBits / downloadTime_i
2. Estimate available bandwidth (harmonic mean
   of the last 5 samples — punishes recent drops
   harder than a plain average):
     T_est = n / Σ(1 / T_i)
3. Apply a safety margin m (< 1 = conservative):
     capacity = T_est × m
4. Pick the highest ladder rung with
     bitrate(rung) ≤ capacity
5. Buffer‑based override: if buffer < 5 s,
   force the lowest rung regardless of (4) —
   protect against a stall over raw quality.

Buffer is seconds of already‑downloaded playback waiting to be shown. It rises by one chunk‑duration each time a chunk finishes, and drains in real time during playback. It caps at 30 s — a full client won't keep prefetching.
Rebuffer / stall happens when buffer hits 0 before the next chunk arrives; playback pauses and only resumes once ~2 s has re‑buffered. Each 0‑hit is counted once as one event.
The chart on the right runs this same adaptive stream side‑by‑side against a naive Always Max stream fed the identical bandwidth trace, so the rebuffer‑event counters below are a genuine, measured comparison, not scripted numbers.

This is the same family of algorithm (throughput‑rule + buffer‑rule) used by real HLS/DASH players and CDN‑backed mobile apps to keep rich content smooth without over‑ or under‑spending a user's mobile data budget.

⏸ REBUFFERING

Buffer level (Adaptive) Buffer level (Always Max) Selected bitrate (Adaptive)