Recherche avancée
Autres articles (112)
-
Personnaliser en ajoutant son logo, sa bannière ou son image de fond
5 septembre 2013, parCertains thèmes prennent en compte trois éléments de personnalisation : l’ajout d’un logo ; l’ajout d’une bannière l’ajout d’une image de fond ;
-
Websites made with MediaSPIP
2 mai 2011, parThis page lists some websites based on MediaSPIP.
-
Creating farms of unique websites
13 avril 2011, parMediaSPIP platforms can be installed as a farm, with a single "core" hosted on a dedicated server and used by multiple websites.
This allows (among other things) : implementation costs to be shared between several different projects / individuals rapid deployment of multiple unique sites creation of groups of like-minded sites, making it possible to browse media in a more controlled and selective environment than the major "open" (...)
Sur d’autres sites (14628)
-
VP8 Codec Optimization Update
16 juin 2010, par noreply@blogger.com (John Luther) — inside webmSince WebM launched in May, the team has been working hard to make the VP8 video codec faster. Our community members have contributed improvements, but there’s more work to be done in some interesting areas related to performance (more on those below).
Encoder
The VP8 encoder is ripe for speed optimizations. Scott LaVarnway’s efforts in writing an x86 assembly version of the quantizer will help in this goal significantly as the quantizer is called many times while the encoder makes decisions about how much detail from the image will be transmitted.For those of you eager to get involved, one piece of low-hanging fruit is writing a SIMD version of the ARNR temporal filtering code. Also, much of the assembly code only makes use of the SSE2 instruction set, and there surely are newer extensions that could be made use of. There are also redundant code removal and other general cleanup to be done ; (Yaowu Xu has submitted some changes for these).
At a higher level, someone can explore some alternative motion search strategies in the encoder. Eventually the motion search can be decoupled entirely to allow motion fields to be calculated elsewhere (for example, on a graphics processor).Decoder
Decoder optimizations can bring higher resolutions and smoother playback to less powerful hardware.Jeff Muizelaar has submitted some changes which combine the IDCT and summation with the predicted block into a single function, helping us avoid storing the intermediate result, thus reducing memory transfers and avoiding cache pollution. This changes the assembly code in a fundamental way, so we will need to sync the other platforms up or switch them to a generic C implementation and accept the performance regression. Johann Koenig is working on implementing this change for ARM processors, and we’ll merge these changes into the mainline soon.
In addition, Tim Terriberry is attacking a different method of bounds checking on the "bool decoder." The bool decoder is performance-critical, as it is called several times for each bit in the input stream. The current code handles this check with a simple clamp in the innermost loops and a less-frequent copy into a circular buffer. This can be expensive at higher data rates. Tim’s patch removes the circular buffer, but uses a more complex clamp in the innermost loops. These inner loops have historically been troublesome on embedded platforms.
To contribute in these efforts, I’ve started working on rewriting higher-level parts of the decoder. I believe there is an opportunity to improve performance by paying better attention to data locality and cache layout, and reducing memory bus traffic in general. Another area I plan to explore is improving utilization in the multi-threaded decoder by separating the bitstream decoding from the rest of the image reconstruction, using work units larger than a single macroblock, and not tying functionality to a specific thread. To get involved in these areas, subscribe to the codec-devel mailing list and provide feedback on the code as it’s written.Embedded Processors
We want to optimize multiple platforms, not just desktops. Fritz Koenig has already started looking at the performance of VP8 on the Intel Atom platform. This platform need some attention as we wrote our current x86 assembly code with an out-of-order processor in mind. Since Atom is an in-order processor (much like the original Pentium), the instruction scheduling of all of the x86 assembly code needs to be reexamined. One option we’re looking at is scheduling the code for the Atom processor and seeing if that impacts the performance on other x86 platforms such as the Via C3 and AMD Geode. This is shaping up to be a lot of work, but doing it would provide us with an opportunity to tighten up our assembly code.
These issues, along with wanting to make better use of the larger register file on x86_64, may reignite every assembly programmer’s (least ?) favorite debate : whether or not to use intrinsics. Yunqing Wang has been experimenting with this a bit, but initial results aren’t promising. If you have experience in dealing with a lot of assembly code across several similar-but-kinda-different platforms, these maintainability issues might be familiar to you. I hope you’ll share your thoughts and experiences on the codec-devel mailing list.
Optimizing codecs is an iterative (some would say never-ending) process, so stay tuned for more posts on the progress we’re making, and by all means, start hacking yourself.
It’s exciting to see that we’re starting to get substantial code contributions from developers outside of Google, and I look forward to more as WebM grows into a strong community effort.
John Koleszar is a software engineer at Google. -
On-demand and seamless transcoding of individual HLS segments
5 janvier 2024, par Omid AriyanBackground


I've been meaning to implement on-demand transcoding of certain video formats such as ".mkv", ".wmv", ".mov", etc. in order to serve them on a media management server using ASP.NET Core 6.0, C# and ffmpeg.


My Approach


The approach I've decided to use is to serve a dynamically generated .m3u8 file which is simply generated using a segment duration of choice e.g. 10s and the known video duration. Here's how I've done it. Note that the resolution is currently not implemented and discarded :


public string GenerateVideoOnDemandPlaylist(double duration, int segment)
{
 double interval = (double)segment;
 var content = new StringBuilder();

 content.AppendLine("#EXTM3U");
 content.AppendLine("#EXT-X-VERSION:6");
 content.AppendLine(String.Format("#EXT-X-TARGETDURATION:{0}", segment));
 content.AppendLine("#EXT-X-MEDIA-SEQUENCE:0");
 content.AppendLine("#EXT-X-PLAYLIST-TYPE:VOD");
 content.AppendLine("#EXT-X-INDEPENDENT-SEGMENTS");

 for (double index = 0; (index * interval) < duration; index++)
 {
 content.AppendLine(String.Format("#EXTINF:{0:#.000000},", ((duration - (index * interval)) > interval) ? interval : ((duration - (index * interval)))));
 content.AppendLine(String.Format("{0:00000}.ts", index));
 }

 content.AppendLine("#EXT-X-ENDLIST");

 return content.ToString();
}

[HttpGet]
[Route("stream/{id}/{resolution}.m3u8")]
public IActionResult Stream(string id, string resolution)
{
 double duration = RetrieveVideoLengthInSeconds();
 return Content(GenerateVideoOnDemandPlaylist(duration, 10), "application/x-mpegURL", Encoding.UTF8);
}


Here's an example of how the .m3u8 file looks like :


#EXTM3U
#EXT-X-VERSION:6
#EXT-X-TARGETDURATION:10
#EXT-X-MEDIA-SEQUENCE:0
#EXT-X-PLAYLIST-TYPE:VOD
#EXT-X-INDEPENDENT-SEGMENTS
#EXTINF:10.000000,
00000.ts
#EXTINF:3.386667,
00001.ts
#EXT-X-ENDLIST


So the player would ask for 00000.ts, 00001.ts, etc. and the next step is to have them generated on demand :


public byte[] GenerateVideoOnDemandSegment(int index, int duration, string path)
{
 int timeout = 30000;
 int totalWaitTime = 0;
 int waitInterval = 100;
 byte[] output = Array.Empty<byte>();
 string executable = "/opt/homebrew/bin/ffmpeg";
 DirectoryInfo temp = Directory.CreateDirectory(System.IO.Path.Combine(System.IO.Path.GetTempPath(), System.IO.Path.GetRandomFileName()));
 string format = System.IO.Path.Combine(temp.FullName, "output-%05d.ts");

 using (Process ffmpeg = new())
 {
 ffmpeg.StartInfo.FileName = executable;

 ffmpeg.StartInfo.Arguments = String.Format("-ss {0} ", index * duration);
 ffmpeg.StartInfo.Arguments += String.Format("-y -t {0} ", duration);
 ffmpeg.StartInfo.Arguments += String.Format("-i \"{0}\" ", path);
 ffmpeg.StartInfo.Arguments += String.Format("-c:v libx264 -c:a aac ");
 ffmpeg.StartInfo.Arguments += String.Format("-segment_time {0} -reset_timestamps 1 -break_non_keyframes 1 -map 0 ", duration);
 ffmpeg.StartInfo.Arguments += String.Format("-initial_offset {0} ", index * duration);
 ffmpeg.StartInfo.Arguments += String.Format("-f segment -segment_format mpegts {0}", format);

 ffmpeg.StartInfo.CreateNoWindow = true;
 ffmpeg.StartInfo.UseShellExecute = false;
 ffmpeg.StartInfo.RedirectStandardError = false;
 ffmpeg.StartInfo.RedirectStandardOutput = false;

 ffmpeg.Start();

 do
 {
 Thread.Sleep(waitInterval);
 totalWaitTime += waitInterval;
 }
 while ((!ffmpeg.HasExited) && (totalWaitTime < timeout));

 if (ffmpeg.HasExited)
 {
 string filename = System.IO.Path.Combine(temp.FullName, "output-00000.ts");

 if (!File.Exists(filename))
 {
 throw new FileNotFoundException("Unable to find the generated segment: " + filename);
 }

 output = File.ReadAllBytes(filename);
 }
 else
 {
 // It's been too long. Kill it!
 ffmpeg.Kill();
 }
 }

 // Remove the temporary directory and all its contents.
 temp.Delete(true);

 return output;
}

[HttpGet]
[Route("stream/{id}/{index}.ts")]
public IActionResult Segment(string id, int index)
{
 string path = RetrieveVideoPath(id);
 return File(GenerateVideoOnDemandSegment(index, 10, path), "application/x-mpegURL", true);
}
</byte>

So as you can see, here's the command I use to generate each segment incrementing -ss and -initial_offset by 10 for each segment :


ffmpeg -ss 0 -y -t 10 -i "video.mov" -c:v libx264 -c:a aac -segment_time 10 -reset_timestamps 1 -break_non_keyframes 1 -map 0 -initial_offset 0 -f segment -segment_format mpegts /var/folders/8h/3xdhhky96b5bk2w2br6bt8n00000gn/T/4ynrwu0q.z24/output-%05d.ts


The Problem


Things work on a functional level, however the transition between segments is slightly glitchy and especially the audio has very short interruptions at each 10 second mark. How can I ensure the segments are seamless ? What can I improve in this process ?


-
Alfresco fails to create video thumbnail
17 octobre 2019, par DeckardAs error log says :
Empty input file ...It turned out that the source image forImageMagickis zero sized. (/data/was/alfresco/tomcat/temp/Alfresco/ImageMagickContentTransformerWorker_source_8718262212685093199.jpg). When I manually replace the source image to normal image and execute the command again, there’s no error.command: /data/was/alfresco/common/bin/convert /data/was/alfresco/tomcat/temp/Alfresco/ImageMagickContentTransformerWorker_source_8718262212685093199.jpg[0] -auto-orient -resize "100x100>" -strip -quiet /data/was/alfresco/tomcat/temp/Alfresco/ImageMagickContentTransformerWorker_target_7652060684136589026.pngSo I think the source image is maybe made by
FFMPEGby capturing some frame of the video.
And theFFMPEGsomehow failed to do it. Not sure my guess is right...But my
FFMPEGworks good asffmpeg -versionshows proper version info. AndFFMPEGis run byrootand the Alfresco daemon instance is run byroot. It seems that there’s nothing wrong.Please review it. Here’s the whole Alfresco-share log :
Caused by: org.alfresco.service.cmr.repository.ContentIOException: 09160037 Content conversion failed:
reader: ContentAccessor[ contentUrl=store:///data/was/alfresco/tomcat/temp/Alfresco/ComplextTransformer_intermediate_mp4_262176879279399174.jpg, mimetype=image/jpeg, size=0, encoding=UTF-8, locale=en_US]
writer: ContentAccessor[ contentUrl=store:///data/was/alfresco/tomcat/temp/Alfresco/FailoverTransformer_intermediate_ComplexContentTransformer_5223852355212570043.png, mimetype=image/png, size=0, encoding=UTF-8, locale=en_US]
options: {use=doclib, contentReaderNodeRef=null, contentWriterNodeRef=null, sourceContentProperty=null, imageAutoOrient=true, targetContentProperty=null, commandOptions=, imageResizeOptions=ImageResizeOptions [width=100, height=100, maintainAspectRatio=true, percentResize=false, resizeToThumbnail=false, allowEnlargement=false], includeEmbedded=null}
limits: {timeoutMs=120000, pageLimit=1}
at org.alfresco.repo.content.transform.AbstractContentTransformer2.transform(AbstractContentTransformer2.java:350)
at org.alfresco.repo.content.transform.ComplexContentTransformer.transformInternal(ComplexContentTransformer.java:492)
at org.alfresco.repo.content.transform.AbstractContentTransformer2.transform(AbstractContentTransformer2.java:272)
... 32 more
Caused by: org.alfresco.service.cmr.repository.ContentIOException: 09160036 Failed to perform ImageMagick transformation:
Execution result:
os: Linux
command: /data/was/alfresco/common/bin/convert /data/was/alfresco/tomcat/temp/Alfresco/ImageMagickContentTransformerWorker_source_8718262212685093199.jpg[0] -auto-orient -resize "100x100>" -strip -quiet /data/was/alfresco/tomcat/temp/Alfresco/ImageMagickContentTransformerWorker_target_7652060684136589026.png
succeeded: false
exit code: 1
out:
err: .convert.bin: Empty input file `/data/was/alfresco/tomcat/temp/Alfresco/ImageMagickContentTransformerWorker_source_8718262212685093199.jpg' @ error/jpeg.c/JPEGErrorHandler/331.
.convert.bin: NoImageForProperty "%w" @ warning/property
at org.alfresco.repo.content.transform.magick.ImageMagickContentTransformerWorker.transformInternal(ImageMagickContentTransformerWorker.java:205)
at org.alfresco.repo.content.transform.magick.AbstractImageMagickContentTransformerWorker.transform(AbstractImageMagickContentTransformerWorker.java:284)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.alfresco.repo.management.subsystems.SubsystemProxyFactory$1.invoke(SubsystemProxyFactory.java:79)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204)
at com.sun.proxy.$Proxy28.transform(Unknown Source)
at org.alfresco.repo.content.transform.ProxyContentTransformer.transformInternal(ProxyContentTransformer.java:107)
at org.alfresco.repo.content.transform.AbstractContentTransformer2.transform(AbstractContentTransformer2.java:272)
... 34 moreIn alfresco-global.properties :
ffmpeg.exe=/usr/local/bin/ffmpeg/ffmpeg* Update As Robert suggested, TransFormer log level changed to debug.
But the log is too long to paste here. There’s 30,000 characters limit of body in SO which github doesn’t have.
So please refer to github issue, I pasted the log there.
https://github.com/Alfresco/share/issues/127
Syndiquer tout le site
