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• FFMPEG - modify only part of video with select filter

  28 janvier 2023, par Compact

  I have a video file - an NTSC DVD rip. I want to convert it into PAL DVD. The problem with that NTSC DVD is that it's a mixture of telecined content, true progressive 29.97 content, true interlaced content at 29.97 fps. The problem is with the true interlaced content - it's sometimes encoded as top field first and sometimes as bottom field first...

  


  To keep quality as much as possible, I would like remove telecined frames, but keep those interlaced sequences and turn them to 25 fps top field first. This is where the problem arises.

  


  I tried to make filter_complex chain with two select filters, where I reverse the fields for bottom field first frames, but the video is not encoding at all when I do that.

  


  Here is an example filter chain I tried to make - I've made a lot of iterations of something similar, using select or metadata select to no avail. I guess I don't understand how select and metadata select filters work. And I don't know how to do what I want.

  


  ffmpeg -i "input" -flags +ildct+ilme \
-filter_complex\
[0:v]idet,setparams=color_primaries=smpte170m:color_trc=bt709:colorspace=smpte170m \
,metadata=select:key=lavfi.idet.single.current_frame:value=bff:function=same_str,phase=b[bot];\[bot]metadata=select:key=lavfi.idet.single.current_frame:value=tff:function=same_str\
,fieldmatch=mode=pcn_ub:combmatch=full,decimate[tff];\
[tff]metadata=select:key=lavfi.idet.single.current_frame:value=progressive:function=same_str\
,fps=24000/1001[v1];[v1]select,setfield=tff[v]"


  


  If all of the interlaced content was top field first, I could simply do something similar to this :

  


  ffmpeg -i "input" -flags +ildct+ilme \
-filter:v "dejudder,fps=30000/1001,fieldmatch=mode=pcn_ub:combmatch=full,\
decimate,settb=1/25000,setpts=N/(25*TB),setfield=tff,setparams=field_mode=tff"


  


  Is that possible with ffmpeg ? To just modify a part of video and then modify it whole, including with the previous modification ?

  


• Get image from webcam, convert that image into something else, and returning it back to the client

  29 janvier 2023, par immigration9

  I have some questions on choosing the right architectural decision to solve my problem.

  


  I am planning to create an app, which takes the

  


  


  1. input from a client's (a browser) webcam,

     


  


  2. sending the input to the server (whether frame by frame, or just live stream video)

     


  


  3. getting each frame from the server (into a image)

     


  


  4. convert the image using some technology (let's say like a tiktok filter)

     


  


  5. returning the image back to the client in real time.

     


  


  


  Except for the phase 4 which the technology can only be applied on an image,
Everything else can be changed.

  


  I'm targeting 30fps (or at least 20) with 1080p quality.

  


  The language or framework is completely agnostic as I do not have any preference. Right now, I am thinking of using React with Node, but I'm opened to other options as well. (eg. Python maybe. Language doesn't matter)

  


  If anyone have some prior experiences, can you teach me the best way ?

  


  I've tried to create the image blob from client and send it to the server using socket.io but it seemed too slow to use when targeted at 30fps on 1080p image.

  


  I'm currently looking at WebRTC with fluent-ffmpeg, but not sure if it's the right way.

  


  Any kind of help will be appreciated.

  


• In what way does this HEVC video not comply to Apples's requirements document ?

  16 novembre 2022, par Duke Dougal

  My goal is to work out why a given video file does not play on Macos/Safari/Quicktime.

  


  The background to this question is that it is possible to play HEVC videos with a transparent background/alpha channel on Safari/MacOS. To be playable, a video must meet the specific requirements set out by Apple in this document :

  


  https://developer.apple.com/av-foundation/HEVC-Video-with-Alpha-Interoperability-Profile.pdf

  


  The video that does not play on Apple/Safari/Quicktime is an HEVC video with an alpha transparency channel. Note that VLC for MacOS DOES play this file. Here it is :

  


  https://drive.google.com/file/d/1ZnXjcDbk-_YxTgRuH_D7RSR9SXdY_XTv/view?usp=share_link

  


  I have two example HEVC video files with a transparent background/alpha channel, and they both play fine using either Quicktime player or Safari :

  


  Working video #1 :

  


  https://drive.google.com/file/d/1PJAyg_sVKVvb-Py8PAu42c1qm8l2qCbh/view?usp=share_link

  


  Working video #2 :

  


  https://drive.google.com/file/d/1kk8ssUyT7qAaK15afp8VPR6mIWPFX8vQ/view?usp=sharing

  


  The first step is to work out in what way my non-working video ( https://drive.google.com/file/d/1ZnXjcDbk-_YxTgRuH_D7RSR9SXdY_XTv/view?usp=share_link ) does not comply with the specification.

  


  Once it is clear which requirements are not met by the non-working video then I can move onto the next phase, which is to try to formulate an ffmpeg command that will output a video meeting the requirements.

  


  I have read Apples requirements document and I am out of my depth in trying to analyse the non working video against the requirements - I don't know how to do it.

  


  Can anyone suggest a way to identify what is wrong with the video ?

  


  Additional context is that I am trying to find a way to create Apple/MacOS compatible alpha channel / transparent videos using ffmpeg with hevc_nvenc running on an Intel machine. I am aware that Apple hardware can create such videos, but for a wide variety of reasons it is not practical for me to use Apple hardware to do the job. I have spent many hours trying all sorts of ffmpeg and ffprobe commands to try to work out what is wrong and modify the video to fix it, but to be honest most of my attempts are guesswork.