Accelerate scan for start codes by skipping up to 3 bytes per iteration.
A start code prefix is defined by the following bytes: 00 00 01. Thus,
for any group of 3 bytes (xx yy zz), we have the following possible cases:
1. If zz != 1, this cannot be a start code, then skip 3 bytes;
2. If yy != 0, this cannot be a start code, then skip 2 bytes;
3. If xx != 0 or zz != 1, this cannot be a start code, then skip 1 byte;
4. xx == 00, yy == 00, zz == 1, we have match!
This algorithm requires to peek bytes from the adapter. This increases the
amount of bytes copied to a temporary buffer, but this process is much faster
than scanning for all the bytes and using shift/masks. So, overall, this is
a win.
Move parsing back to decoding step, but keep functions separate for now.
This is needed for future optimizations that may introduce some meta data
for parsed info attached to codec frames.
Optimize pre-allocation of decoder units, thus avoiding un-necessary
memory reallocations. The heuristic used is that we could have around
one slice unit per macroblock line.
Use a GArray to hold decoder units in a frame, instead of a single-linked
list. This makes 'append' calls faster, but not that much. At least, this
makes things clearer.
Allocate decoder unit earlier in the main parse() function and don't
delegate this task to derived classes. The ultimate purpose is to get
rid of dynamic allocation of decoder units.
The SPS, PPS and slice headers are not fully zero-initialized in the
codecparsers/ library. Rather, the standard upstream behaviour is to
initialize only certain syntax elements with some inferred values if
they are not present in the bitstream.
At the gstreamer-vaapi decoder level, we need to further initialize
certain syntax elements with some sensible default values so that to
not complicate VA drivers that just pass those verbatim to the HW,
and also avoid an memset() of the whole decoder unit.
Signed-off-by: Sreerenj Balachandran <sreerenj.balachandran@intel.com>
Signed-off-by: Gwenole Beauchesne <gwenole.beauchesne@intel.com>
Make GstVaapiVideoBuffer a simple wrapper for video meta. This buffer is
no longer necessary but for compatibility with GStreamer 0.10 APIs or users
expecting a GstSurfaceBuffer like Clutter.
Use PTS value computed by the decoder, which could also be derived from
the GstVideoCodecFrame PTS. This makes it possible to fix up the PTS if
the original one was miscomputed or only represented a DTS instead.
Create a new VA context if the encoded surface size changes because we
need to keep the underlying surface pool until the last one was released.
Otherwise, either of the following cases could have happened: (i) release
a VA surface to an inexistent pool, or (ii) release VA surface to an
existing surface pool, but with different size.
Avoid creating a GstBuffer for slice data. Rather, directly use the codec
frame input buffer data. This is possible because the codec frame is valid
until end_frame() where we submit the VA buffers for decoding. Anyway, the
slice data buffer is copied into the VA buffer when it is created.
Implement GstVaapiDecoder.start_frame() and end_frame() semantics so
that to create new VA context earlier and submit VA pictures to the
HW for decoding as soon as possible. i.e. don't wait for the next
frame to start decoding the previous one.
Parse slice() header and first macroblock position earlier in _parse()
function instead of waiting for the _decode() stage. This doesn't change
anything but readability.
Introduce new GstVaapiDecoderUnitMpeg2 object, which holds the standard
GstMpegVideoPacket and additional parsed header info. Besides, we now
parse as early as in the _parse() function so that to avoid un-necessary
creation of sub-buffers in _decode() for video packets that are not slices.
Theory of operations: all units marked as "slice" are moved to the "units"
list. Since this list only contains slice data units, the prev_slice pointer
was removed. Besides, we now maintain two extra lists of units to be decoded
before or after slice data units.
In particular, all units in the "pre_units" list will be decoded before
GstVaapiDecoder::start_frame() is called and units in the "post_units"
list will be decoded after GstVaapiDecoder::end_frame() is called.
Make GstVaapiSurfaceProxy only a thin wrapper around a VA context and a
VA surface. i.e. drop any other attribute like timestamp, duration,
interlaced or top-field-first.
Maintain decoded surfaces as GstVideoCodecFrame objects instead of
GstVaapiSurfaceProxy objects. The latter will tend to be reduced to
the strict minimum: a context and a surface.
Add new gst_vaapi_decoder_get_frame() function meant to be used with
gst_vaapi_decoder_decode(). The purpose is to return the next decoded
frame as a GstVideoCodecFrame and the associated GstVaapiSurfaceProxy
as the user-data object.
Decoder units were zero-initialized, including the SPS/PPS/slice headers.
The latter don't require zero-initialization since the codecparsers/ lib
will do so for key variables already. This is not a great value per se but
at least it makes it possible to check whether the default initialization
decisions made in the codecparsers/ lib were right or not.
This can be reverted if this exposes too many issues.
Drop explicit initialization of most fields that are implicitly set to
zero. Drop helper macros for casting to GstVaapiPictureH264 or
GstVaapiFrameStore. Also remove some useless checks for NULL pointers.
Implement GstVaapiDecoder.start_frame() and end_frame() semantics so
that to create new VA context earlier and submit VA pictures to the
HW for decoding as soon as possible. i.e. don't wait for the next
frame to start decoding the previous one.
Introduce new GstVaapiDecoderUnitH264 object, which holds the standard
NAL unit header (GstH264NalUnit) and additional parsed header info.
Besides, we now parse headers as early as in the _parse() function so
that to avoid un-necessary creation of sub-buffers in _decode() for
NAL units that are not slices.
This is a performance win by ~+1.1% only.
Use standard GstVideoCodecState throughout GstVaapiDecoder and expose
it with a new gst_vaapi_decoder_get_codec_state() function. This makes
it possible to drop picture size (width, height) information, framerate
(fps_n, fps_d) information, pixel aspect ratio (par_n, par_d) information,
and interlace mode (is_interlaced field).
This is a new API with backwards compatibility maintained. In particular,
gst_vaapi_decoder_get_caps() is still available.
Signed-off-by: Sreerenj Balachandran <sreerenj.balachandran@intel.com>
Signed-off-by: Gwenole Beauchesne <gwenole.beauchesne@intel.com>
Align gst_vaapi_decoder_get_surface() semantics with the rest of the
API. That is, return a GstVaapiDecoderStatus and the decoded surface
as a handle to GstVaapiSurfaceProxy in parameter.
This is an API/ABI change.
Introduce new decoding process whereby a GstVideoCodecFrame is created
first. Next, input stream buffers are accumulated into a GstAdapter,
that is then passed to the _parse() function. The GstVaapiDecoder object
accumulates all parsed units and when a complete frame or field is
detected, that GstVideoCodecFrame is passed to the _decode() function.
Ultimately, the caller receives a GstVaapiSurfaceProxy if decoding
process was successful.
The start_frame() hook is called prior to traversing all decode-units
for decoding. The unit argument represents the first slice in the frame.
Some codecs (e.g. H.264) need to wait for the first slice in order to
determine the actual VA context parameters.
Split decoding process into two steps: (i) parse incoming bitstreams
into simple decoder-units until the frame or field is complete; and
(ii) decode the whole frame or field at once.
This is an ABI change.
