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Autres articles (93)
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Configuration spécifique pour PHP5
4 février 2011, parPHP5 est obligatoire, vous pouvez l’installer en suivant ce tutoriel spécifique.
Il est recommandé dans un premier temps de désactiver le safe_mode, cependant, s’il est correctement configuré et que les binaires nécessaires sont accessibles, MediaSPIP devrait fonctionner correctement avec le safe_mode activé.
Modules spécifiques
Il est nécessaire d’installer certains modules PHP spécifiques, via le gestionnaire de paquet de votre distribution ou manuellement : php5-mysql pour la connectivité avec la (...) -
Les formats acceptés
28 janvier 2010, parLes commandes suivantes permettent d’avoir des informations sur les formats et codecs gérés par l’installation local de ffmpeg :
ffmpeg -codecs ffmpeg -formats
Les format videos acceptés en entrée
Cette liste est non exhaustive, elle met en exergue les principaux formats utilisés : h264 : H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10 m4v : raw MPEG-4 video format flv : Flash Video (FLV) / Sorenson Spark / Sorenson H.263 Theora wmv :
Les formats vidéos de sortie possibles
Dans un premier temps on (...) -
Les autorisations surchargées par les plugins
27 avril 2010, parMediaspip core
autoriser_auteur_modifier() afin que les visiteurs soient capables de modifier leurs informations sur la page d’auteurs
Sur d’autres sites (6025)
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Gettting silence level to be used with silencedetect automatically
3 mai 2017, par P. DeeMy goal is to find the average or maximum silent level in dB to use it with
silencedetect
. I foundvolumedetect
and I thought to use thehistogram_
results to find the lowest dB numbers(low as in -40dB, -50dB etc.) with a high number of occurrences.What is a better idea ? Can it be combined with the silencedetect command, so I don’t need to enter the dB-Value at all ?
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vc-1 : Optimise parser (with special attention to ARM)
21 juillet 2014, par Ben Avisonvc-1 : Optimise parser (with special attention to ARM)
The previous implementation of the parser made four passes over each input
buffer (reduced to two if the container format already guaranteed the input
buffer corresponded to frames, such as with MKV). But these buffers are
often 200K in size, certainly enough to flush the data out of L1 cache, and
for many CPUs, all the way out to main memory. The passes were :1) locate frame boundaries (not needed for MKV etc)
2) copy the data into a contiguous block (not needed for MKV etc)
3) locate the start codes within each frame
4) unescape the data between start codesAfter this, the unescaped data was parsed to extract certain header fields,
but because the unescape operation was so large, this was usually also
effectively operating on uncached memory. Most of the unescaped data was
simply thrown away and never processed further. Only step 2 - because it
used memcpy - was using prefetch, making things even worse.This patch reorganises these steps so that, aside from the copying, the
operations are performed in parallel, maximising cache utilisation. No more
than the worst-case number of bytes needed for header parsing is unescaped.
Most of the data is, in practice, only read in order to search for a start
code, for which optimised implementations already existed in the H264 codec
(notably the ARM version uses prefetch, so we end up doing both remaining
passes at maximum speed). For MKV files, we know when we’ve found the last
start code of interest in a given frame, so we are able to avoid doing even
that one remaining pass for most of the buffer.In some use-cases (such as the Raspberry Pi) video decode is handled by the
GPU, but the entire elementary stream is still fed through the parser to
pick out certain elements of the header which are necessary to manage the
decode process. As you might expect, in these cases, the performance of the
parser is significant.To measure parser performance, I used the same VC-1 elementary stream in
either an MPEG-2 transport stream or a MKV file, and fed it through avconv
with -c:v copy -c:a copy -f null. These are the gperftools counts for
those streams, both filtered to only include vc1_parse() and its callees,
and unfiltered (to include the whole binary). Lower numbers are better :Before After
File Filtered Mean StdDev Mean StdDev Confidence Change
M2TS No 861.7 8.2 650.5 8.1 100.0% +32.5%
MKV No 868.9 7.4 731.7 9.0 100.0% +18.8%
M2TS Yes 250.0 11.2 27.2 3.4 100.0% +817.9%
MKV Yes 149.0 12.8 1.7 0.8 100.0% +8526.3%Yes, that last case shows vc1_parse() running 86 times faster ! The M2TS
case does show a larger absolute improvement though, since it was worse
to begin with.This patch has been tested with the FATE suite (albeit on x86 for speed).
Signed-off-by : Luca Barbato <lu_zero@gentoo.org>
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Copy frame specific properties (eg. width and height)
5 août 2014, par gkuczeraIt’s not that something is not working, I just can’t figure out how to copy frame props (eg. height and width) after usage of sws_scale function - this function doesn’t copy them into the destination frame).
Why I need this ? My frame after scaling is becoming the input for the filter, and it’s source props have to be specified to specific numbers, not like it accepts everything (so a frame with width and height equal to zero - which I get after scaling - is not an option).
I tried to use
av_frame_copy_props
but even in this function’s description, they mentioned that it will not do this.
Here is the code :
AVFrame* tOwnersFrame = pOwner->getFrame();
AVFrame* tResizedFrame = avcodec_alloc_frame();
int tResizedFrameWidth = pMaxFrameWidth;
int tResizedFrameHeight = pMaxFrameHeight;
if (!tResizedFrame)
{
cout << "Couldn't allocate the frame!" << endl;
return;
}
uint8_t* tBuffer;
int tBytesNeeded;
tBytesNeeded = avpicture_get_size(PIX_FMT_RGB24, tResizedFrameWidth, tResizedFrameHeight);
tBuffer = (uint8_t*)av_malloc(tBytesNeeded * sizeof(uint8_t));
avpicture_fill((AVPicture*)tResizedFrame, tBuffer, PIX_FMT_RGB24, tResizedFrameWidth, tResizedFrameHeight);
mSwsContext = sws_getCachedContext(mSwsContext, pOwner->getFrameWidth(), pOwner->getFrameHeight(), AV_PIX_FMT_BGR24, tResizedFrameWidth, tResizedFrameHeight, PIX_FMT_RGB24, SWS_BILINEAR, NULL, NULL, NULL);
sws_scale(mSwsContext, (const uint8_t* const *)tOwnersFrame->data, tOwnersFrame->linesize, 0, pOwner->getFrameHeight(), tResizedFrame->data, tResizedFrame->linesize);
cout << "FramesMerger::resizeFrameMax - arg frame size: " << pOwner->getFrame()->width << ", " << pOwner->getFrame()->height << endl;
cout << "FramesMerger::resizeFrameMax - resized frame size: " << tResizedFrame->width << ", " << tResizedFrame->height << endl;