Hi all, Thanks for the quick replies!
On 11 June 2014 05:54, Gwenole Beauchesne <[email protected]> wrote: > Hi, > > 2014-06-10 20:33 GMT+02:00 Sam Jansen <[email protected]>: > > > I've been working on H264 encode, decode, and JPEG decode VA-API programs > > recently, using the Intel va-driver on Sandy Bridge and Bay Trail. > > > > This has gone well, but I've hit a problem with the H264 decoder in some > > situations where I believe it is producing incorrect output. In some > cases > > chroma, and less often luma, data does not agree with the reference > decoder > > [1], often in Intra frames (but sometimes P frames too), always baseline > > profile. I have an intra-encoded test stream where the 389th frame of a > > stream encoded from the standard "paris (cif)" test stream is incorrect > on > > both Sandy Bridge and Bay Trail. Many other test streams pass fine, > leaving > > me to believe our decoder implementation is largely correct. > > > > I've also implemented a mode where I am able to get the current encoded > > picture out of the VA-API encoder. I can then compare this, > byte-for-byte, > > against a decode of the frame just encoded. I use this with out software > > codecs to ensure our encode and decode match exactly. Using this > technique I > > can easily compare our software codec, and the VA-API H264 codecs in any > > combination. I've found the VA-API encode always agrees with our decoder, > > but the VA-API decoder does not always agree with the encode - either our > > software encoder or the VA-API encoder (this testing just on Bay Trail). > > > > I'd like to get to the bottom of this. The first step is removing our > decode > > implementation from the test, and using one you believe to be good. What > > tools do you use for regression testing? Is this perhaps ffmpeg invoked > in > > some way? Is your test setup open source, such that I can modify it to > > include my new test stream? > > The supported HW decoders that use VA-API and can be serve as > reference are either GStreamer/vaapi, or FFmpeg/vaapi (for H.264). > <http://gitorious.org/vaapi/gstreamer-vaapi/> > > Please provide me with a sample. We also have other tools, which I > will publish later on. > > I've made it temporarily available at: http://cam.starleaf.com/paris_cif_intra.264 Feel free to have a look at it. You're welcome to add it to whatever test suite you have as well. However, I'm happy right now that I should first use your gstreamer-vaapi to decode it, and check I get the same result there. I would have thought the most likely explanation at this point in time is that I have a bug in my VA-API H264 decoder -- I'd rather you didn't waste your time on my bugs! > > PS: here's an extract of some of the chroma bytes where it has gone > right. > > On the top, some bytes of reference decoder output, on the bottom, bytes > of > > VA-API H264 decoder output. Note the 0x8f83 becomes 0x908f, then 0x8e8e > > becomes 0x8d8d, the 0x8e8e becomes 0x8d8e. > > Note: how do you retrieve the bytes for comparison? If this is through > vaGetImage(), the result of the conversion is generally not bitexact. > > I use vaDeriveImage(), which gives me a VA_FOURCC_NV12 image. I then vaMapBuffer() it to get at the image data. > Regards, > Gwenole. >
_______________________________________________ Libva mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/libva
