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La conservation du net art au musée. Les stratégies à l’œuvre
26 mai 2011
Mis à jour : Juillet 2013
Langue : français
Type : Texte
Autres articles (53)
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Gestion générale des documents
13 mai 2011, parMédiaSPIP ne modifie jamais le document original mis en ligne.
Pour chaque document mis en ligne il effectue deux opérations successives : la création d’une version supplémentaire qui peut être facilement consultée en ligne tout en laissant l’original téléchargeable dans le cas où le document original ne peut être lu dans un navigateur Internet ; la récupération des métadonnées du document original pour illustrer textuellement le fichier ;
Les tableaux ci-dessous expliquent ce que peut faire MédiaSPIP (...) -
Publier sur MédiaSpip
13 juin 2013Puis-je poster des contenus à partir d’une tablette Ipad ?
Oui, si votre Médiaspip installé est à la version 0.2 ou supérieure. Contacter au besoin l’administrateur de votre MédiaSpip pour le savoir -
Des sites réalisés avec MediaSPIP
2 mai 2011, parCette page présente quelques-uns des sites fonctionnant sous MediaSPIP.
Vous pouvez bien entendu ajouter le votre grâce au formulaire en bas de page.
Sur d’autres sites (7871)
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Watch My Hero Academia Heroes Rising Full Movie Online FREE #2019
6 juillet 2020, par sarahlburke58Watch My Hero Academia : Heroes Rising (2018) Full Movie Online HD Streaming Free Unlimited Download, Watch My Hero Academia : Heroes Rising (2018) Full Series 2017 Online Movie for Free DVD Rip Full HD With English Subtitles Ready For Download.


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Title : My Hero Academia : Heroes Rising
Release : 2019-12-20
Runtime : 104 min
Genre : Animation, Action
Stars : Daiki Yamashita, Nobuhiko Okamoto, Kenta Miyake, Ayane Sakura, Aoi Yuki, Yuki Kaji


Overview : Class 1-A visits Nabu Island where they finally get to do some real hero work. The place is so peaceful that it's more like a vacation … until they're attacked by a villain with an unfathomable Quirk ! His power is eerily familiar, and it looks like Shigaraki had a hand in the plan. But with All Might retired and citizens' lives on the line, there's no time for questions. Deku and his friends are the next generation of heroes, and they're the island's only hope.


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How to avoid stopping or record all dynamic videos in the process of capturing screen video with ffmpeg from a python program ?
3 décembre 2020, par fengnixI have many robotframework test cases and in the first case, a ffmpeg command like the following is invoked to record the whole running process :


ffmpeg -framerate 30 -f gdigrab -i desktop -c:v libx264rgb -crf 0 -preset ultrafast output.mkv



Whenever I firstly run all cases and then manuually run the above command from an addition command console, the recorded video always looks fine, it looks like all contents on the screen can be correctly captured.


However, once I execute the command the same as the above one in the first case by call the following code :


p=subprocess.Popen(cmd, shell=True, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE)



and then in the final test case the record process is stopped by calling the following code to tell ffmpeg that we want to stop the recording :


p.stdin.write(bytes("q",'UTF-8')) 



the final result video only contain correct contents of the "start" and the "end" of the whole process, but all other contents no longer changed and seemd just a static image, which means all the dynamic effects on the screen cannot be captured.


Could anyone be so kind as to let me know what the matter is and how to solve it ?


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ffmpeg h264 to mp4 conversion from multiple files fails to preserve in-sequence resolution changes
1er juillet 2023, par LB2This will be a long post, so I thank you in advance for your patience in digesting it.


Context


I have different sources that generate visual content that eventually need to be all composed into a single .mp4 file. The sources are :


- 

- H.264 video (encoded using CUDA NVENC).

- 

- This video can have in-sequence resolution change that is natively supported by H.264 codec.
- I.e. stream may start as HxW resolution and mid-stream change to WxH. This behavior happens because it comes from a camera device that can be rotated and flipped between portrait and landscape (e.g. think of a phone camera recording video and phone being flipped from one orientation to another, and video recording adjusting its encoding for proper video scaling and orientation).
- When rotation occurs, most of the time H & W are just swaps, but may actually be entirely new values — e.g. in some cases 1024x768 will switch to 768x1024, but in other cases 1024x768 may become 460x640 (depends on source camera capabilities that I have no control over).








- JPEGs. A series (a.k.a. batch) of still JPEGs.

- 

- The native resolution of JPEGs may or may not match the video resolution in the earlier bullet.
- JPEGs can also reflect rotation of device and so some JPEGs in a sequence may start at HxW resolution and then from some arbitrary JPEG file can flip and become WxH. Similar to video, resolution dimensions are likely to be just a swap, but may become altogether different values.






- There can be any number of batches and intermixes between video and still sources. E.g. V1 + S2 + S3 + V4 + V5 + V6 + S7 + ...
- There can be any number of resolution changes between or within batches. e.g. V1 ;r1 + V1 ;r2 + S2 ;r1 + S2 ;r3 + V3 ;r2 + ... (where first subscript is batch sequence ; rX is resolution)










Problem


I'm attempting to do this conversion with
ffmpeg
and can't quite get it right. The problem is that I can't get output to respect source resolutions, and it just squishes all into a single output resolution.



As already mentioned above, H.264 supports resolution changes in-sequence (mid-stream), and it should be possible to convert and concatenate all the content and have final output contain in-sequence resolution changes.


Since MP4 is just a container, I'm assuming that MP4 files can do so as well ?


Attempts so far


The approach thus far has been to take each batch of content (i.e. .h264 video or a set of JPEGs), and individually convert to .mp4. Video is converted using
-c copy
to ensure it doesn't try to transcode, e.g. :

ffmpeg -hide_banner -i videoX.h264 -c copy -vsync vfr -video_track_timescale 90000 intermediateX.mp4



... and JPEGs are converted using
-f concat


ffmpeg -hide_banner -f concat -safe 0 -i jpegsX.txt -vf 'scale=trunc(iw/2)*2:trunc(ih/2)*2' -r 30 -vsync vfr -video_track_timescale 90000 intermediateX.mp4



... and then all the intermediates concatenated together


ffmpeg -hide_banner -f concat -safe 0 -i final.txt -pix_fmt yuv420p -c copy -vsync vfr -video_track_timescale 90000 -metadata title='yabadabadoo' -fflags +bitexact -flags:v +bitexact -flags:a +bitexact final.mp4



This concatenates, but if resolution changes at some mid point, then that part of content comes up squished/stretched in final output.


Use h.264 as intermediates


All the intermediates are produced the same, except as .h264. All intermediate .h264 are
cat
'ed together like `cat intermediate1.h264 intermediate2.264 > final.h264.

If final output is
final.mp4
, the output is incorrect and images are squished/stretched.

If
final.h264
, then at least it seems to be respecting aspect ratios of input and managing to produce correctly looking output. However, examining withffprobe
it seems that it uses SAR weird ratios, where first frames arewidth=1440 height=3040 sample_aspect_ratio=1:1
, but later SAR takes on values likewidth=176 height=340 sample_aspect_ratio=1545:176
, which I suspect isn't right, since all original input was with "square pixels". I think the reason for it is that it was composed out of different sized JPEGs, and concat filter somehow caused ffmpeg to manipulate SAR "to get things fit".

But at least it renders respectably, though hard to say with
ffplay
if player would actually see resolution change and resize accordingly .

And, that's .h264 ; and I need final output to be .mp4.


Use
-vf
filter

I tried enforcing SAR using
-vf 'scale=trunc(iw/2)*2:trunc(ih/2)*2,setsar=1:1'
(scaling is to deal with odd dimension JPEGs), but it still produces frames with SAR like stated earlier.

Other thoughts


For now, while I haven't given up, I'm trying to avoid in my code examining each individual JEPG in a batch to see if there are differing sizes, and splitting batch so that each sub-batch is homogenous resolution-wise, and generating individual intermediate .h264 so that SAR remains sane, and keep fingers crossed that the final would work correctly. It'll be very slow, unfortunately.


Question


What's the right way to deal with all that using
ffmpeg
, and how to concatenate mulitple varying resolution sources into a final mp4 so that it respects resolution changes mid-stream ?

- H.264 video (encoded using CUDA NVENC).