UserAgent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/54.0.2840.71 Safari/537.36

Steps to reproduce the problem:
1. Set up an Asterisk server that relays video on SIP calls and that accepts SIP over WebSockets on at least one SIP test account.
2. Create an internal extension in the Asterisk server that just plays an audio file then hangs up.
3. Set up a webpage with SIP.js 0.7.5 that uses <video> tags as its rendering targets. Open this webpage on a machine with a webcam available for the browser, as well as a microphone and headphones/speakers.
4. Make a call from the browser, using the SIP account on step 1, with rendering constraints that specify audio-only. This should work correctly, as it does on Firefox 49 (the other browser), and play the audio file.
5. Repeat the test in step 4, but with rendering constraints that specify both audio and video.

What is the expected behavior?
The <video> tag used as the remote render target should start playing the received audio while displaying nothing, in all cases. This is what happens when the rendering constraints specify audio-only on both Chromium and Firefox, and is also what happens with video-enabled rendering constraints on Firefox.

What went wrong?
The <video> tag for remote target does not play any sound.

Did this work before? N/A 

Does this work in other browsers? Yes

Chrome version: 54.0.2840.71  Channel: stable
OS Version: 4.7.9-200.fc24.x86_64
Flash Version: Shockwave Flash 23.0 r0

Discussion in SIP.js forums at: https://groups.google.com/forum/#!topic/sip_js/5joLWQ0zJDI

The highlights:
If the web page constraints media to audio-only, the call plays audio successfully.
If the web page specifies video in media constraints, but there is no webcam present, the call plays audio successfully.
If the web page specifies video, and makes a video call to a SIP destination that receives video, both audio and video are transmitted successfully.
On the failing case, the microphone on the Chromium side does transmit audio that is heard on the other side of the connected call.

The exchanged SDP bodies are available at the discussion linked above, and are also cited below, for a video call originated from Chrome browser to an audio-only extension:

INVITE sip:2002@elx4-2.elastix.palosanto.com SIP/2.0 
Via: SIP/2.0/WSS 192.0.2.120;branch=z9hG4bK6497336 
Max-Forwards: 70 
To: <sip:2002@elx4-2.elastix.palosanto.com> 
From: "Alex Villacís Lasso" <sip:1064@elx4-2.elastix.palosanto.com>;tag=au4hjlo5ja 
Call-ID: r4it5okggvd5n4of7jfl 
CSeq: 8127 INVITE 
Authorization: Digest algorithm=MD5, username="1064", realm="asterisk", nonce="31819bae", uri="sip:2002@elx4-2.elastix.palosanto.com", response="b355aa6e96b41b4948e91a470ef27f72" 
Contact: <sip:b7bcflgi@192.0.2.120;transport=wss;ob> 
Allow: ACK,CANCEL,INVITE,MESSAGE,BYE,OPTIONS,INFO,NOTIFY,REFER 
Content-Type: application/sdp 
Supported: 100rel, outbound 
User-Agent: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 
Content-Length: 5316 

v=0 
o=- 4220688008494682042 2 IN IP4 127.0.0.1 
s=- 
t=0 0 
a=group:BUNDLE audio video 
a=msid-semantic: WMS PHxaZ9dcoefxQT5gNqY8TGxUkzsuIYR8y3MA 
m=audio 50993 UDP/TLS/RTP/SAVPF 111 103 104 9 0 8 106 105 13 126 
c=IN IP4 201.234.196.170 
a=rtcp:54522 IN IP4 201.234.196.170 
a=candidate:3356704504 1 udp 2122260223 10.2.0.1 51101 typ host generation 0 network-id 2 network-cost 50 
a=candidate:3700057831 1 udp 2122194687 192.168.3.2 50993 typ host generation 0 network-id 1 
a=candidate:3356704504 2 udp 2122260222 10.2.0.1 52330 typ host generation 0 network-id 2 network-cost 50 
a=candidate:3700057831 2 udp 2122194686 192.168.3.2 54522 typ host generation 0 network-id 1 
a=candidate:2257633800 1 tcp 1518280447 10.2.0.1 9 typ host tcptype active generation 0 network-id 2 network-cost 50 
a=candidate:2450102807 1 tcp 1518214911 192.168.3.2 9 typ host tcptype active generation 0 network-id 1 
a=candidate:2257633800 2 tcp 1518280446 10.2.0.1 9 typ host tcptype active generation 0 network-id 2 network-cost 50 
a=candidate:2450102807 2 tcp 1518214910 192.168.3.2 9 typ host tcptype active generation 0 network-id 1 
a=candidate:1976953138 1 udp 1685987071 201.234.196.170 50993 typ srflx raddr 192.168.3.2 rport 50993 generation 0 network-id 1 
a=candidate:1976953138 2 udp 1685987070 201.234.196.170 54522 typ srflx raddr 192.168.3.2 rport 54522 generation 0 network-id 1 
a=ice-ufrag:O5G2 
a=ice-pwd:rO4XOTR3IXYOG7/FesonVFCT 
a=fingerprint:sha-256 82:28:E1:6F:20:EB:DE:62:BB:FA:FF:96:01:0A:E0:36:FE:70:67:24:F7:E5:C1:7A:71:29:9B:DF:0F:77:E3:C1 
a=setup:actpass 
a=mid:audio 
a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level 
a=extmap:3 http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time 
a=sendrecv 
a=rtcp-mux 
a=rtpmap:111 opus/48000/2 
a=rtcp-fb:111 transport-cc 
a=fmtp:111 minptime=10;useinbandfec=1 
a=rtpmap:103 ISAC/16000 
a=rtpmap:104 ISAC/32000 
a=rtpmap:9 G722/8000 
a=rtpmap:0 PCMU/8000 
a=rtpmap:8 PCMA/8000 
a=rtpmap:106 CN/32000 
a=rtpmap:105 CN/16000 
a=rtpmap:13 CN/8000 
a=rtpmap:126 telephone-event/8000 
a=ssrc:896535526 cname:wQg5BI6BYQVEHvL5 
a=ssrc:896535526 msid:PHxaZ9dcoefxQT5gNqY8TGxUkzsuIYR8y3MA 67592eb3-5d47-4e31-abe7-eb3b94e59a63 
a=ssrc:896535526 mslabel:PHxaZ9dcoefxQT5gNqY8TGxUkzsuIYR8y3MA 
a=ssrc:896535526 label:67592eb3-5d47-4e31-abe7-eb3b94e59a63 
m=video 57794 UDP/TLS/RTP/SAVPF 100 101 107 116 117 96 97 99 98 
c=IN IP4 201.234.196.170 
a=rtcp:40294 IN IP4 201.234.196.170 
a=candidate:3356704504 1 udp 2122260223 10.2.0.1 49330 typ host generation 0 network-id 2 network-cost 50 
a=candidate:3700057831 1 udp 2122194687 192.168.3.2 57794 typ host generation 0 network-id 1 
a=candidate:3356704504 2 udp 2122260222 10.2.0.1 59657 typ host generation 0 network-id 2 network-cost 50 
a=candidate:3700057831 2 udp 2122194686 192.168.3.2 40294 typ host generation 0 network-id 1 
a=candidate:2257633800 1 tcp 1518280447 10.2.0.1 9 typ host tcptype active generation 0 network-id 2 network-cost 50 
a=candidate:2450102807 1 tcp 1518214911 192.168.3.2 9 typ host tcptype active generation 0 network-id 1 
a=candidate:2257633800 2 tcp 1518280446 10.2.0.1 9 typ host tcptype active generation 0 network-id 2 network-cost 50 
a=candidate:2450102807 2 tcp 1518214910 192.168.3.2 9 typ host tcptype active generation 0 network-id 1 
a=candidate:1976953138 1 udp 1685987071 201.234.196.170 57794 typ srflx raddr 192.168.3.2 rport 57794 generation 0 network-id 1 
a=candidate:1976953138 2 udp 1685987070 201.234.196.170 40294 typ srflx raddr 192.168.3.2 rport 40294 generation 0 network-id 1 
a=ice-ufrag:O5G2 
a=ice-pwd:rO4XOTR3IXYOG7/FesonVFCT 
a=fingerprint:sha-256 82:28:E1:6F:20:EB:DE:62:BB:FA:FF:96:01:0A:E0:36:FE:70:67:24:F7:E5:C1:7A:71:29:9B:DF:0F:77:E3:C1 
a=setup:actpass 
a=mid:video 
a=extmap:2 urn:ietf:params:rtp-hdrext:toffset 
a=extmap:3 http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time 
a=extmap:4 urn:3gpp:video-orientation 
a=extmap:6 http://www.webrtc.org/experiments/rtp-hdrext/playout-delay 
a=sendrecv 
a=rtcp-mux 
a=rtcp-rsize 
a=rtpmap:100 VP8/90000 
a=rtcp-fb:100 ccm fir 
a=rtcp-fb:100 nack 
a=rtcp-fb:100 nack pli 
a=rtcp-fb:100 goog-remb 
a=rtcp-fb:100 transport-cc 
a=rtpmap:101 VP9/90000 
a=rtcp-fb:101 ccm fir 
a=rtcp-fb:101 nack 
a=rtcp-fb:101 nack pli 
a=rtcp-fb:101 goog-remb 
a=rtcp-fb:101 transport-cc 
a=rtpmap:107 H264/90000 
a=rtcp-fb:107 ccm fir 
a=rtcp-fb:107 nack 
a=rtcp-fb:107 nack pli 
a=rtcp-fb:107 goog-remb 
a=rtcp-fb:107 transport-cc 
a=fmtp:107 level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=42e01f 
a=rtpmap:116 red/90000 
a=rtpmap:117 ulpfec/90000 
a=rtpmap:96 rtx/90000 
a=fmtp:96 apt=100 
a=rtpmap:97 rtx/90000 
a=fmtp:97 apt=101 
a=rtpmap:99 rtx/90000 
a=fmtp:99 apt=107 
a=rtpmap:98 rtx/90000 
a=fmtp:98 apt=116 
a=ssrc-group:FID 908615762 2952703772 
a=ssrc:908615762 cname:wQg5BI6BYQVEHvL5 
a=ssrc:908615762 msid:PHxaZ9dcoefxQT5gNqY8TGxUkzsuIYR8y3MA 6df7b062-cac6-4361-a182-cd123053131d 
a=ssrc:908615762 mslabel:PHxaZ9dcoefxQT5gNqY8TGxUkzsuIYR8y3MA 
a=ssrc:908615762 label:6df7b062-cac6-4361-a182-cd123053131d 
a=ssrc:2952703772 cname:wQg5BI6BYQVEHvL5 
a=ssrc:2952703772 msid:PHxaZ9dcoefxQT5gNqY8TGxUkzsuIYR8y3MA 6df7b062-cac6-4361-a182-cd123053131d 
a=ssrc:2952703772 mslabel:PHxaZ9dcoefxQT5gNqY8TGxUkzsuIYR8y3MA 
a=ssrc:2952703772 label:6df7b062-cac6-4361-a182-cd123053131d 

SIP/2.0 200 OK 
Via: SIP/2.0/WSS 192.0.2.120;branch=z9hG4bK6497336;received=127.0.0.1;rport=53932 
From: "Alex Villacís Lasso" <sip:1064@elx4-2.elastix.palosanto.com>;tag=au4hjlo5ja 
To: <sip:2002@elx4-2.elastix.palosanto.com>;tag=as7bf95094 
Call-ID: r4it5okggvd5n4of7jfl 
CSeq: 8127 INVITE 
Server: FPBX-2.11.0(11.23.1) 
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY, INFO, PUBLISH, MESSAGE 
Supported: replaces, timer 
Contact: <sip:2002@201.234.196.170:0;transport=WS> 
Content-Type: application/sdp 
Content-Length: 2044 

v=0 
o=root 1832220046 1832220046 IN IP4 201.234.196.170 
s=Asterisk PBX 11.23.1 
c=IN IP4 201.234.196.170 
b=CT:384 
t=0 0 
m=audio 13742 UDP/TLS/RTP/SAVPF 8 0 9 111 126 
a=rtpmap:8 PCMA/8000 
a=rtpmap:0 PCMU/8000 
a=rtpmap:9 G722/8000 
a=rtpmap:111 opus/48000/2 
a=maxptime:60 
a=fmtp:111 maxplaybackrate=16000; stereo=0; sprop-stereo=0; useinbandfec=0 
a=rtpmap:126 telephone-event/8000 
a=fmtp:126 0-16 
a=ptime:20 
a=ice-ufrag:61e8f77a148083ea7ee6279873e77414 
a=ice-pwd:4d39bab53edd3aee532dc1d352097a54 
a=candidate:Ha020002 1 UDP 2130706431 10.2.0.2 13742 typ host 
a=candidate:Hc0a805c3 1 UDP 2130706431 192.168.5.195 13742 typ host 
a=candidate:Sc9eac4aa 1 UDP 1694498815 201.234.196.170 13742 typ srflx raddr 10.2.0.2 rport 13742 
a=candidate:Ha020002 2 UDP 2130706430 10.2.0.2 13743 typ host 
a=candidate:Hc0a805c3 2 UDP 2130706430 192.168.5.195 13743 typ host 
a=candidate:Sc9eac4aa 2 UDP 1694498814 201.234.196.170 13743 typ srflx raddr 10.2.0.2 rport 13743 
a=connection:new 
a=setup:active 
a=fingerprint:SHA-256 04:68:E8:54:FF:8E:B8:EA:6B:9C:4C:FA:5D:09:C0:53:20:30:B1:98:1F:11:8F:ED:54:DF:F5:23:60:87:85:93 
a=sendrecv 
m=video 15360 UDP/TLS/RTP/SAVPF 100 99 98 
a=ice-ufrag:248acbee2dad9451034301e422fa185f 
a=ice-pwd:43999af807144b2d3dc5ca16273ea048 
a=candidate:Ha020002 1 UDP 2130706431 10.2.0.2 15360 typ host 
a=candidate:Hc0a805c3 1 UDP 2130706431 192.168.5.195 15360 typ host 
a=candidate:Sc9eac4aa 1 UDP 1694498815 201.234.196.170 15360 typ srflx raddr 10.2.0.2 rport 15360 
a=candidate:Ha020002 2 UDP 2130706430 10.2.0.2 15361 typ host 
a=candidate:Hc0a805c3 2 UDP 2130706430 192.168.5.195 15361 typ host 
a=candidate:Sc9eac4aa 2 UDP 1694498814 201.234.196.170 15361 typ srflx raddr 10.2.0.2 rport 15361 
a=connection:new 
a=setup:active 
a=fingerprint:SHA-256 04:68:E8:54:FF:8E:B8:EA:6B:9C:4C:FA:5D:09:C0:53:20:30:B1:98:1F:11:8F:ED:54:DF:F5:23:60:87:85:93 
a=rtpmap:100 VP8/90000 
a=rtcp-fb:100 ccm fir 
a=rtpmap:99 H264/90000 
a=rtpmap:98 H263-1998/90000 
a=fmtp:98 F=0;I=0;J=0;T=0;K=0;N=0;BPP=0;HRD=0 
a=sendrecv