Up until now, an initialized MpegEncContext had an array of
MPVPictures (way more than were ever needed) and the MPVPicture*
contained in the MPVWorkPictures as well as the input_picture
and reordered_input_picture arrays (for the encoder) pointed
into this array. Several of the pointers could point to the
same slot and because there was no reference counting involved,
one had to check for aliasing before unreferencing.
Furthermore, given that these pointers were not ownership pointers
the pointers were often simply reset without unreferencing
the slot (happened e.g. for the RV30 and RV40 decoders) or
there were moved without resetting the src pointer (happened
for the encoders where the entries in the input_picture
and reordered_input_picture arrays were not reset).
Instead actually releasing these pictures was performed by looping
over the whole array and checking which one of the entries needed
to be kept. Given that the array had way too many slots (36),
this meant that more than 30 MPVPictures have been unnecessarily
unreferenced in every ff_mpv_frame_start(); something similar
happened for the encoder.
This commit changes this by making the MPVPictures refcounted
via the RefStruct API. The MPVPictures itself are part of a pool
so that this does not entail constant allocations; instead,
the amount of allocations actually goes down, because the
earlier code used such a large array of MPVPictures (36 entries) and
allocated an AVFrame for every one of these on every
ff_mpv_common_init(). In fact, the pool is only freed when closing
the codec, so that reinitializations don't lead to new allocations
(this avoids having to sync the pool in update_thread_context).
Making MPVPictures refcounted also has another key benefit:
It makes it possible to directly share them across threads
(when using frame-threaded decoding), eliminating ugly code
with underlying av_frame_ref()'s; sharing these pictures
can't fail any more.
The pool is allocated in ff_mpv_decode_init() for decoders,
which therefore can fail now. This and the fact that the pool
is not unreferenced in ff_mpv_common_end() also necessitated
to mark several mpegvideo-decoders with the FF_CODEC_CAP_INIT_CLEANUP
flag.
*: This also means that there is no good reason any more for
ff_mpv_common_frame_size_change() to exist.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Currently identical to the H.261 and H.263 close functions
(which it replaces). It will be extended in future commits.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This brings it in line with mpeg12dec.c.
(This entry has been added before the MPEG2VIDEO codec id
existed.)
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This is all that is used. This is in preparation for further
commits that will extend ff_mpv_decode_init() in a way
that will make it possible to fail and require cleanup.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
It already avoids a goto and will be useful in the future
to be able to specify each functions tasks and obligations.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
There are two types of MPVPictures: Three (cur_pic, last_pic, next_pic)
that are directly part of MpegEncContext and an array of MPVPictures
that are separately allocated and are mostly accessed via pointers
(cur|last|next)_pic_ptr; they are also used to store AVFrames in the
encoder (necessary due to B-frames). As the name implies, each of the
former is directly associated with one of the _ptr pointers:
They actually share the same underlying buffers, but the ones
that are part of the context can have their data pointers offset
and their linesize doubled for field pictures.
Up until now, each of these had their own references; in particular,
there was an underlying av_frame_ref() to sync cur_pic and cur_pic_ptr
etc. This is wasteful.
This commit changes this relationship: cur_pic, last_pic and next_pic
now become MPVWorkPictures; this structure does not have an AVFrame
at all any more, but only the cached values of data and linesize.
It also contains a pointer to the corresponding MPVPicture, establishing
a more natural relationsship between the two.
This already means that creating the context-pictures from the pointers
can no longer fail.
What has not been changed is the fact that the MPVPicture* pointers
are not ownership pointers and that the MPVPictures are part of an
array of MPVPictures that is owned by a single AVCodecContext.
Doing so will be done in a latter commit.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This way said function sets everything (except for the actual
contents of the frame's data). Also rename it to prepare_picture()
given its new role.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
ff_alloc_picture() currently does two things: It checks the
consistency of the linesize (which should not be necessary, but is)
and it allocates certain buffers. (It does not actually allocate
the picture buffers, so its name is misleading.)
This commit splits it into two separate functions. The rationale
for this is that for the encoders, every picture needs its linesizes
checked, but not every picture needs these extra buffers.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Make it clear that this is not a failure of get_buffer/the user,
but a deficit of mpegvideo.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Specifically, add const to the pointed-to-type of pointers
that point to something static or that belong to last_pic
or next_pic (because modifying these might lead to data races).
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Use the cached values from MpegEncContext.(cur|last|next)_pic
instead of the corresponding *_pic_ptr.
Also do the same in wmv2dec.c and mpegvideo_enc.c.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This avoids an indirection and is in preparation for removing
the AVFrame from MpegEncContext.(cur|last|next)_pic altogether.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
No mpegvideo based codec supports alpha.
While just at it, also make the define shorter.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
current_picture->cur_pic, last_picture->last_pic, similarly
for new_picture and next_picture.
Also rename the corresponding *_ptr fields.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
It is the only user of said table and doing so is especially
important given that this buffer is zeroed every time.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
It involves less allocations and therefore has less
potential errors to be checked. One consequence thereof
is that updating the picture tables can no longer fail.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This avoids constant allocations+frees and will also allow
to simply switch to the RefStruct API, thereby avoiding
the overhead of the AVBuffer API.
It also simplifies the code, because it removes the "needs_realloc"
field: It was added in 435c0b87d2,
before the introduction of the AVBuffer API: given that these buffers
may be used by different threads, they were not freed immediately
and instead were marked as being freed later by setting needs_realloc.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
VC-1 can switch from between being progressive and interlaced
on a per-frame basis. In the latter case, the number of macroblocks
is aligned to two (or equivalently, the height to 32); therefore
certain buffers are allocated for the bigger mb_height
(see 950fb8acb4 and
017e234c20).
This commit changes how this is done: Aligning these buffers is
restricted to VC-1 and it is done directly by aligning
mb_height (but not MpegEncContext.mb_height) instead of
adding something in an ad-hoc manner.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Codecs call ff_find_unused_picture() to get the index of
an unused picture; said picture may have buffers left
from using it previously (these buffers are intentionally
not unreferenced so that it might be possible to reuse them;
they are only reused when they are writable, otherwise
they are replaced by new, zeroed buffers). They should
not make any assumptions about which picture they get.
Yet this is not true for mbskip_table and damaged bitstreams.
When one returns old unused slots randomly, the output
becomes nondeterministic. This can't happen now (see below),
but it will be possible once mpegpicture uses proper pools
for the picture tables.
The following discussion uses the sample created via
ffmpeg -bitexact -i fate-suite/svq3/Vertical400kbit.sorenson3.mov -ps 50 -bf 2 -bitexact -an -qscale 5 -ss 40 -error_rate 4 -threads 1 out.avi
When decoding this with one thread, the slots are as follows:
Cur 0 (type I), last -1, Next -1; cur refcount -1, not reusing buffers
Cur 1 (type P), last -1, Next 0; cur refcount -1, not reusing buffers
Cur 2 (type B), last 0, Next 1; cur refcount -1, not reusing buffers
Cur 2 (type B), last 0, Next 1; cur refcount 2, not reusing buffers
Cur 0 (type P), last 0, Next 1; cur refcount 2, not reusing buffers
Cur 2 (type B), last 1, Next 0; cur refcount 1, reusing buffers
Cur 2 (type B), last 1, Next 0; cur refcount 2, not reusing buffers
Cur 1 (type P), last 1, Next 0; cur refcount 2, not reusing buffers
Cur 2 (type B), last 0, Next 1; cur refcount 1, reusing buffers
Cur 2 (type B), last 0, Next 1; cur refcount 2, not reusing buffers
Cur 0 (type I), last 0, Next 1; cur refcount 2, not reusing buffers
Cur 2 (type B), last 1, Next 0; cur refcount 1, reusing buffers
Cur 2 (type B), last 1, Next 0; cur refcount 2, not reusing buffers
Cur 1 (type P), last 1, Next 0; cur refcount 2, not reusing buffers
After the slots have been filled initially, the buffers are only
reused for the first B-frame in a B-frame chain:
a) When the new picture is an I or a P frame, the slot of the backward
reference is cleared and reused for the new frame (as has been said,
"cleared" does not mean that the auxiliary buffers have been
unreferenced). Given that not only the slot in the picture array,
but also MpegEncContext.last_picture contain references to these
auxiliary buffers, they are not writable and are therefore not reused,
but replaced by new, zero-allocated buffers.
b) When the new picture is the first B-frame in a B-frame chain,
the two reference slots are kept as-is and one gets a slot that
does not share its auxiliary buffers with any of MpegEncContext.
current_picture, last_picture, next_picture. The buffers are
therefore writable and are reused.
c) When the new picture is a B-frame that is not the first frame
in a B-frame chain, ff_mpv_frame_start() reuses the slot occupied
by the preceding B-frame. Said slot shares its auxilary buffers
with MpegEncContext.current_picture, so that they are not considered
writable and are therefore not reused.
When using frame-threading, the slots are made to match the one
from the last thread, so that the above analysis is mostly the same
with one exception: Other threads may also have references to these
buffers, so that initial B-frames of a B-frame chain need no longer
have writable/reusable buffers. In particular, all I and P-frames
always use new, zeroed buffers. Because only the mbskip_tables of
I- and P-frames are ever used, it follows that there is currently
no problem with using stale values for them at all.
Yet as the analysis shows this is very fragile:
1. MpegEncContext.(current|last|next)_picture need not have
references of their own, but they have them and this influences
the writability decision.
2. It would not work if the slots were returned in a truely random
fashion or if there were a proper pool used.
Therefore this commit always resets said buffer. This is in preparation
for actually adding such a pool (where the checksums for said sample
would otherwise be depending on the number of threads used for
decoding).
Future commits will restrict this to only the codecs for which
it is necessary (namely the MPEG-4 decoder).
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Codecs call ff_find_unused_picture() to get the index of
an unused picture; said picture may have buffers left
from using it previously (these buffers are intentionally
not unreferenced so that it might be possible to reuse them;
this is mpegvideo's version of a bufferpool). They should
not make any assumptions about which picture they get.
Yet somehow this is not true when decoding OBMC: Returning
random empty pictures (instead of the first one) leads
to nondeterministic results; similarly, explicitly
rezeroing the buffer before handing it over to the codec
changes the outcome of the h263-obmc tests, but it makes it
independent of the returned pictures. Therefore this commit
does so.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
coded_block is only used for I-frames, so it is unnecessary
to reset it in ff_clean_intra_table_entries() (which
cleans certain tables for a non-intra MB).
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
When !CONFIG_SMALL, we create separate functions for FMT_MPEG1
(i.e. for MPEG-1/2); given that there are only three possibilities
for out_format (FMT_MPEG1, FMT_H263 and FMT_H261 -- MJPEG and SpeedHQ
are both intra-only and do not have motion vectors at all, ergo
they don't call this function), one can optimize MPEG-1/2-only code
away in mpeg_motion_internal().
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
These references now always exist due to dummy frames.
Also remove the corresponding checks in the lowres code
in mpegvideo_dec.c.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
MPEG-2 allows to pair an intra field (as first field) together
with a P-field. In this case a conformant bitstream has to satisfy
certain restrictions in order to ensure that only the I field
is used for prediction. See section 7.6.3.5 of the MPEG-2
specifications.
We do not check these restrictions; normally we simply allocate
dummy frames for reference in order to avoid checks lateron.
This happens in ff_mpv_frame_start() and therefore does not happen
for a second field. This is inconsistent. Fix this by allocating
these dummy frames for the second field, too.
This already fixes two bugs:
1. Undefined pointer arithmetic in prefetch_motion() in
mpegvideo_motion.c where it is simply presumed that the reference
frame exists.
2. Several MPEG-2 hardware accelerations rely on last_picture
being allocated for P pictures and next picture for B pictures;
e.g. VDPAU returns VDP_STATUS_INVALID_HANDLE when decoding
an I-P fields pair because the forward_reference was set incorrectly.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This will allow to reuse it to allocate dummy frames for
the second field (which can be a P-field even if the first
field was an intra field).
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
linesize and uvlinesize are supposed to be the common linesize of all
the Y/UV-planes of all the currently cached pictures.
ff_mpeg_update_thread_context() syncs the pictures, yet it did not sync
linesize and uvlinesize. This mostly works, because ff_alloc_picture()
only accepts new pictures if they coincide with the linesize of the
already provided pictures (if any). Yet there is a catch: Linesize
changes are accepted when the dimensions change (in which case the
cached frames are discarded).
So imagine a scenario where all frame threads use the same dimension A
until a frame with a different dimension B is encountered in the
bitstream, only to be instantly reverted to A in the next picture. If
the user changes the linesize of the frames upon the change to dimension
B and keeps the linesize thereafter (possible if B > A),
ff_alloc_picture() will report an error when frame-threading is in use:
The thread decoding B will perform a frame size change and so will the
next thread in ff_mpeg_update_thread_context() as well as when decoding
its picture. But the next thread will (presuming it is not the same
thread that decoded B, i.e. presuming >= 3 threads) not perform a frame
size change, because the new frame size coincides with its old frame
size, yet the linesize it expects from ff_alloc_picture() is outdated,
so that it errors out.
It is also possible for the user to use the original linesizes for
the frame after the frame that reverted back to A; this will be
accepted, yet the assumption that of all pictures are the same
will be broken, leading to segfaults.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
The mpegvideo-based codecs currently require the linesize to be
constant (except when the frame dimensions change); one reason
for this is that certain scratch buffers whose size depend on
linesize are only allocated once and are presumed to be correctly
sized if the pointers are != NULL.
This commit changes this by storing the actual linesize these
buffers belong to and reallocating the buffers if it does not
suffice. This is not enough to actually support changing linesizes,
but it is a start. And it is a prerequisite for the next patch.
Also don't emit an error message in case the source ctx's
edge_emu_buffer is unset in ff_mpeg_update_thread_context().
It need not be an error at all; e.g. it is a perfectly normal
state in case a hardware acceleration is used as the scratch
buffers are not allocated in this case (it is easy to run into
this issue with MPEG-4) or if the src context was not initialized
at all (e.g. because the first packet contained garbage).
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Andreas Rheinhardt