[FFmpeg-devel] [RFC] FFmpeg libavcodec/crystalhd.c: Optimize for reduced latency

thomas schorpp thomas.schorpp at gmail.com
Fri Feb 1 03:26:33 CET 2013

On 31.01.2013 21:05, thomas schorpp wrote:
> On 30.01.2013 18:06, Philip Langdale wrote:
>> On Wed, 30 Jan 2013 00:25:14 +0100
>> thomas schorpp <thomas.schorpp at gmail.com> wrote:
>>> Hello,
>>> 1.
>>> Are You all with vdpau now or was it the kernel crashing driver bug
>>> why most crystal HD projects dropped now for about a year? Patch
>>> attached. Seems to work, no more kernel crashes so far. Broadcom
>>> authors and owner of crystalhd @git.linuxtv.org (latest codebase) not
>>> responding, google group left, anybody out there?
>> Hi Tom,
>> Yes, it's a bit of a dead community. I haven't had the time to look
>> seriously at CrystalHD work for a while. It's very time consuming and
>> frustrating at this point - as most of what you're doing is trying to
>> work around lack of information. You can't trust the driver/library to
>> tell you when a frame a ready, or when a new input packet is needed, or
>> whether an output frame is interlaced or not. 80%+ of crystalhd.c is
>> interlaced heuristics!
>> I had some contact with one of the Broadcom engineers back in 2011 and
>> he had said he'd try and get help for all this stuff but he never got
>> back to me and I had less and less time to work on it, so my efforts
>> tailed off. I got the 70015 working well enough for my needs so my
>> personal motivation to fix 70012, which has such different behaviour,
>> was low. I know it can be made to work (see gstreamer plugin, vlc, etc)
>> but it would be a lot of work to adapt the multi-threaded design to
>> an ffmpeg codec.
> I just have a look at and try the Broadcom gstreamer decoder plugin (on debian stable ^^ , don't know yet if it builds at all),
> it's in C and using pthreads and usual multithreading event methods, if it performs better I'll try to port the mechanisms of
> crystalhd/filters/gst/gst-plugin/src/gstbcmdec.c:1371 bcmdec_process_output() ,etc,
> to FFmpeg.

Be careful developing and testing with the Broadcom driver,it just crashed kernel again on the first attempt using transmageddon:
Patch linked above and attached.

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