Recherche avancée

Sur d’autres sites (7396)

• FFMPEG Re-muxing .MKV to MP4\MV4 while retaining Dolby Digital Plus [closed]

  30 décembre 2020, par David F

  I would be grateful if anyone could help me out here. I'm remuxing a large number of video files from .MKV to .MP4\M4V so they play on the Apple platform (including the TV App) without any issues. It has been a bit of a learning curve, but I’m so close now. It's important NOT to convert, but to remux.

  


  I have achieved the ability to remux 4K HDR with Dolby Digital Plus in a .MKV to 4K HDR with Dolby Digtial 5.1. MP4. The issue is retaining the Dolby Digital Plus. This contains the ATMOS information for object based sound.

  


  The media players on Apple reports Dolby Digital Plus for the .MKV and Dolby Digital 5.1 for .MP4

  


  I'm using FFMPEG with the following command :-

  


  ffmpeg -i original.mkv -c:v copy -c:a eac3 -tag:v hvc1 output.mp4

  


  Output from MediaInfo (note .MKV contains only 1 video and 1 audio track)

  


  Audio -----Original.mkv

  


  

  • ID : 2

  


  • Format : E-AC-3 JOC

  


  • Format/Info : Enhanced AC-3 with Joint
Object Coding

  


  • Commercial name : Dolby Digital Plus with Dolby
Atmos

  


  • Codec ID : **A_**EAC3

  


  • Duration : 51 min 51 s

  


  • Bit rate mode : Constant

  


  


  Audio ----- Remuxed .mp4

  


  

  • ID : 2

  


  • Format : E-AC-3

  


  • Format/Info : Enhanced AC-3

  


  • Commercial name : Dolby Digital Plus

  


  • Codec ID : ec-3

  


  • Duration : 51 min 51 s

  


  • Bit rate mode : Constant

  


  


  The remux operation finished in about 1 minute for a 8Gb 4k video file, so we I know there is no reencoding. My theory is the stream is still a E-AC-3 with Joint Object Control, but its marked as a E-AC-3.

  


  I can see that .mp4 can take E-AC-3 Joint Object Control (JOC) with the demo files from Dolby labs.

  


  I've also remuxed an MKV to MKV and able to see the same result. The JOC markings have been removed with FFMPEG

  


  My ask is, does anyone have any knowledge of how to remux and keep Enhanced AC-3 with Joint Object Control with FFMPEG. Does FFMPEG support this ?

  


  Or know if just editing the Format, Format/Info, and Code ID is enough and the sound information in my .MP4\M4V is E-AC-3 JOC. If so can I just edit the media info, if so how ?

  


  I know Dolby Labs to allow free remuxing of Dolby Digital Plus/ Atmos with sample code and information they have uploaded onto Github for developers. I just wonder if FFMPEG supports it

  


  Thanks in advanced.

  


  David

  


• How would I go about packaging an mp3 file into an mp4 container ?

  22 novembre 2020, par Jacob

  So here's the issue that I'm currently having. I need an audio player for iOS that will play mp3. Now at first glance this may seem like a trivial issue, just create an audio tag and give it the URL to the mp3 file. While this technically works, it's basically unusable since iOS needs to download the entire file before starting to play it. This results in a really long wait time when trying to play large mp3 files (could get close to a minute).
So the first thing I tried was to manually mimic the chunking that chrome does for playing mp3 files. I first sent a HEAD request to get the byte length of the audio file. Used that length / duration in seconds to get the average bytes per second and use that data to request chunks based on where the user seeks to. That didn't work since sometimes mp3 files contain metadata that throw off the calculation (like a cover image). Additionally, sometimes mp3 files use VBR (Variable Bit Rate) and then I'm well and truly screwed.

  



  So this lead me to thinking, Safari couldn't possibly require the end user to download an entire mp4 file before playing it. So I took an mp3 file, converted it to mp4 on an online converter and tested my theory out. Voila, it worked. Safari was streaming the mp4 file in chunks and the wait time went to close to 0. Alright, so now all I need to do is convert mp3 files to mp4 files. The problem now is, I have requirement not to use my server for converting these files. I want to offload this expensive operation to the client. After looking around for a bit I found a few wasm libraries to do this, great ! Nope. These wasm libraries are huge (24 MB) and would add an unacceptable amount to my already large bundles files. So this brings me to my question. Is there any way to "trick" safari into thinking that my mp3 file is mp4. What I've tried already :

  



  On input change event -> get the file -> clone it into a new Blob with a mimeType of video/mp4 and then upload that file to the server. Chrome plays this file no problem (probably because it detects it's an mp3 file), on Safari however it's unable to play the file.

  



  So my question is, is there any way to package the mp3 file in an mp4 container (Client Side !important) to "force" Safari into chunking the file.

  


• vulkan : use push descriptors where possible

  22 septembre 2024, par Lynne

  vulkan : use push descriptors where possible
  Push descriptors are in theory slightly faster, but come with
  
  limitations for which we have to check.
  Either way, they're not difficult to implement, so even though
  
  no one should be using peasant-tier descriptors, do it anyway.
  

  • [DH] libavfilter/vf_nlmeans_vulkan.c
  • [DH] libavutil/hwcontext_vulkan.c
  • [DH] libavutil/vulkan.c
  • [DH] libavutil/vulkan.h
  • [DH] libavutil/vulkan_functions.h
  • [DH] libavutil/vulkan_loader.h