UserAgent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Ubuntu Chromium/52.0.2729.3 Chrome/52.0.2729.3 Safari/537.36

Example URL:
http://www.quirksmode.org/html5/tests/video.html

Steps to reproduce the problem:
1. Navigate to a site containing an H.264 Video
2. Try to play the video

What is the expected behavior?
The video plays

What went wrong?
The video doesn't play

Did this work before? Yes Chromium 50.xxx (not sure of exact version number), currently working Chrome 50.0.2661.86

Is it a problem with Flash or HTML5? HTML5

Does this work in other browsers? Yes 

Chrome version: 52.0.2729.3  Channel: dev
OS Version: Ubuntu 16.04
Flash Version: 

When launching from the terminal I see the following output when the video tries to load:

[1:1:0514/231949:ERROR:render_media_log.cc(23)] MediaEvent: PIPELINE_ERROR decoder: not supported

Examining chrome://media-internals and choosing the mp4 video from the test page I linked above gives the following Player Properties:

render_id: 33
player_id: 0
pipeline_state: kStopped
event: WEBMEDIAPLAYER_CREATED
url: http://www.quirksmode.org/html5/videos/big_buck_bunny.mp4
total_bytes: 5510872
streaming: false
single_origin: true
passed_cors_access_check: false
range_header_supported: true
error: FFmpegDemuxer: open context failed
pipeline_error: demuxer: could not open

And the following Log:

00:00:00 00	pipeline_state	kCreated
00:00:00 00	event	WEBMEDIAPLAYER_CREATED
00:00:00 00	url	http://www.quirksmode.org/html5/videos/big_buck_bunny.mp4
00:00:00 05	total_bytes	5510872
00:00:00 05	streaming	false
00:00:00 05	single_origin	true
00:00:00 05	passed_cors_access_check	false
00:00:00 05	range_header_supported	true
00:00:00 05	pipeline_state	kInitDemuxer
00:00:00 13	error	FFmpegDemuxer: open context failed
00:00:00 13	pipeline_state	kStopping
00:00:00 13	pipeline_state	kStopped
00:00:00 13	pipeline_error	demuxer: could not open

So it looks like something is going wrong with the ffmpeg demuxer. This also effects any youtube video played with the html5 player, for those it is specifically complaining about the audio demuxer. Terminal output is identical, but the media-internals log gives (excerpt):

00:00:00 109	found_audio_stream	true
00:00:00 109	audio_codec_name	aac
00:00:00 437	duration	2007.690158
00:00:00 472	info	Video codec: avc1.64002A
00:00:00 472	found_video_stream	true
00:00:00 472	video_codec_name	h264
00:00:00 472	pipeline_state	kInitRenderer
00:00:00 472	error	audio decoder initialization failed
00:00:00 472	pipeline_state	kStopping
00:00:00 472	pipeline_state	kStopped
00:00:00 476	pipeline_error	decoder: not supported
00:00:00 495	event	WEBMEDIAPLAYER_DESTROYED

I can play these videos fine when I download them and use ffplay, so I am thinking if this is an issue with chromium it is not using my systems ffmpeg but a statically linked one? If this is, however, an issue with my setup let me know what I am doing wrong.