WebRTC Video Fails to Play in Chrome Browser

[hsc6320]

📌 Title

ChatGPT-summarized: WebRTC H.264 stream — RTP packets received, DTLS/SRTP OK, but Chrome framesDecoded=0

📌 Summary (Prepared by ChatGPT)

I am sharing the following issue with the help of ChatGPT, which summarized my board logs and browser logs into a clean, structured report for easier analysis.

📌 Problem Overview

I am streaming H.264 video from an embedded Linux board (Eyenix EN675) to Chrome (WebRTC) using a custom libpeer-based implementation.

The WebRTC connection itself is fully successful:

ICE connected

DTLS-SRTP handshake completed

SRTP sessions created

RTP packets arriving continuously on Chrome

However:

Chrome’s framesDecoded never increases (always 0), so video never appears.

This occurs even though RTP packets and bytes increase normally.

📌 Environment

Device: Eyenix EN675 (Linux)

WebRTC stack: libpeer (custom WebRTC implementation)

Codec: H.264 (packetization-mode=1)

Signaling: MQTT → WebSocket → Browser

Direction: Board → Browser (sendonly → recvonly)

Browser: Chrome latest

📌 What Works (Confirmed Good)
✔️ 1. ICE / STUN / DTLS-SRTP handshake

Board log shows:

state: connected → completed
mbedtls_ssl_handshake (ret=0)
Created inbound SRTP session
Created outbound SRTP session
DataChannel sid=1 opened

Browser:

ICE connected
connectionState=connected
ontrack(video)

✔️ 2. Chrome is definitely receiving RTP packets

Browser stats:

[RTP-V] ssrc=1 packets=29 bytes=9148 framesDecoded=0
[RTP-V] ssrc=1 packets=36 bytes=13380 framesDecoded=0

Packets/bytes increase, framesDecoded stays at 0.

✔️ 3. Board is transmitting SPS / PPS / IDR NALUs

Example:

[HEX][SPS_raw] len=29
00 00 00 01 67 42 C0 16 ...

[HEX][PPS_raw] len=8
00 00 00 01 68 CE 0F C8

[FRAME_IDR_raw] len=2035
00 00 00 01 67 ...
00 00 00 01 68 ...
00 00 01 65 ...

RTP:

SPS → nal_type=7 (OK)
PPS → nal_type=8 (OK)

FU-A fragments for IDR:
7C 85 ... (Start fragment)
...
(End fragment not visible in log)

Second IDR is single-NAL:
size=1010 nal_type=5 markbit=1

So SPS/PPS/IDR appear valid.

Critical Symptom
❗ Chrome continuously sends RTCP PLI/FIR

Board log:

RTCP_PSFB 15
RTCP_PSFB 15
RTCP_PSFB 15

But the board does NOT send a new IDR in response.

Because of this:

Chrome never accepts the initial keyframe

Without a valid keyframe, decoder never starts

→ framesDecoded = 0 forever

This matches classic WebRTC “keyframe missing or invalid” behavior.

[sepfy]

Are you using hardware encoder? What's your GOP and SPS/PPS alway sent with IDR frame? Suggest send IDR + SPS/PPS regularly