Recherche avancée

Sur d’autres sites (5919)

• avformat/mov : fix seeking with HEVC open GOP files

  18 février 2022, par Clément Bœsch

  avformat/mov : fix seeking with HEVC open GOP files
  This was tested with medias recorded from an iPhone XR and an iPhone 13.
  Here is how a typical stream looks like in coding order :
      ┌────────┬─────┬─────┬──────────┐
  
      │ sample | PTS | DTS | keyframe |
  
      ├────────┼─────┼─────┼──────────┤
  
      ┊        ┊     ┊     ┊          ┊
  
      │   53   │ 560 │ 510 │    No    │
  
      │   54   │ 540 │ 520 │    No    │
  
      │   55   │ 530 │ 530 │    No    │
  
      │   56   │ 550 │ 540 │    No    │
  
      │   57   │ 600 │ 550 │    Yes   │
  
      │ * 58   │ 580 │ 560 │    No    │
  
      │ * 59   │ 570 │ 570 │    No    │
  
      │ * 60   │ 590 │ 580 │    No    │
  
      │   61   │ 640 │ 590 │    No    │
  
      │   62   │ 620 │ 600 │    No    │
  
      ┊        ┊     ┊     ┊          ┊
  In composition/display order :
      ┌────────┬─────┬─────┬──────────┐
  
      │ sample | PTS | DTS | keyframe |
  
      ├────────┼─────┼─────┼──────────┤
  
      ┊        ┊     ┊     ┊          ┊
  
      │   55   │ 530 │ 530 │    No    │
  
      │   54   │ 540 │ 520 │    No    │
  
      │   56   │ 550 │ 540 │    No    │
  
      │   53   │ 560 │ 510 │    No    │
  
      │ * 59   │ 570 │ 570 │    No    │
  
      │ * 58   │ 580 │ 560 │    No    │
  
      │ * 60   │ 590 │ 580 │    No    │
  
      │   57   │ 600 │ 550 │    Yes   │
  
      │   63   │ 610 │ 610 │    No    │
  
      │   62   │ 620 │ 600 │    No    │
  
      ┊        ┊     ┊     ┊          ┊
  Sample/frame 58, 59 and 60 are B-frames which actually depends on the
  
  key frame (57). Here the key frame is not an IDR but a "CRA" (Clean
  
  Random Access).
  Initially, I thought I could rely on the sdtp box (independent and
  
  disposable samples), but unfortunately :
      sdtp[54] is_leading:0 sample_depends_on:1 sample_is_depended_on:0 sample_has_redundancy:0
  
      sdtp[55] is_leading:0 sample_depends_on:1 sample_is_depended_on:2 sample_has_redundancy:0
  
      sdtp[56] is_leading:0 sample_depends_on:1 sample_is_depended_on:2 sample_has_redundancy:0
  
      sdtp[57] is_leading:0 sample_depends_on:2 sample_is_depended_on:0 sample_has_redundancy:0
  
      sdtp[58] is_leading:0 sample_depends_on:1 sample_is_depended_on:0 sample_has_redundancy:0
  
      sdtp[59] is_leading:0 sample_depends_on:1 sample_is_depended_on:2 sample_has_redundancy:0
  
      sdtp[60] is_leading:0 sample_depends_on:1 sample_is_depended_on:2 sample_has_redundancy:0
  
      sdtp[61] is_leading:0 sample_depends_on:1 sample_is_depended_on:0 sample_has_redundancy:0
  
      sdtp[62] is_leading:0 sample_depends_on:1 sample_is_depended_on:0 sample_has_redundancy:0
  The information that might have been useful here would have been
  
  is_leading, but all the samples are set to 0 so this was unusable.
  Instead, we need to rely on sgpd/sbgp tables. In my case the video track
  
  contained 3 sgpd tables with the following grouping types : tscl, sync
  
  and tsas. In the sync table we have the following 2 entries (only) :
      sgpd.sync[1] : sync nal_unit_type:0x14
  
      sgpd.sync[2] : sync nal_unit_type:0x15
  (The count starts at 1 because 0 carries the undefined semantic, we'll
  
  see that later in the reference table).
  The NAL unit types presented here correspond to :
      libavcodec/hevc.h :    HEVC_NAL_IDR_N_LP       = 20,
  
      libavcodec/hevc.h :    HEVC_NAL_CRA_NUT        = 21,
  In parallel, the sbgp sync table contains the following :
      ┌────┬───────┬─────┐
  
      │ id │ count │ gdi │
  
      ├────┼───────┼─────┤
  
      │  0 │   1   │  1  │
  
      │  1 │   56  │  0  │
  
      │  2 │   1   │  2  │
  
      │  3 │   59  │  0  │
  
      │  4 │   1   │  2  │
  
      │  5 │   59  │  0  │
  
      │  6 │   1   │  2  │
  
      │  7 │   59  │  0  │
  
      │  8 │   1   │  2  │
  
      │  9 │   59  │  0  │
  
      │ 10 │   1   │  2  │
  
      │ 11 │   11  │  0  │
  
      └────┴───────┴─────┘
  The gdi column (group description index) directly refers to the index in
  
  the sgpd.sync table. This means the first frame is an IDR, then we have
  
  batches of undefined frames interlaced with CRA frames. No IDR ever
  
  appears again (tried on a 30+ seconds sample).
  With that information, we can build an heuristic using the presentation
  
  order.
  A few things needed to be introduced in this commit :
  1. min_sample_duration is extracted from the stts : we need the minimal
  
     step between sample in order to PTS-step backward to a valid point
  
  2. In order to avoid a loop over the ctts table systematically during a
  
     seek, we build an expanded list of sample offsets which will be used
  
     to translate from DTS to PTS
  
  3. An open_key_samples index to keep track of all the non-IDR key
  
     frames ; for now it only supports HEVC CRA frames. We should probably
  
     add BLA frames as well, but I don't have any sample so I prefered to
  
     leave that for later
  It is entirely possible I missed something obvious in my approach, but I
  
  couldn't come up with a better solution. Also, as mentioned in the diff,
  
  we could optimize is_open_key_sample(), but the linear scaling overhead
  
  should be fine for now since it only happens in seek events.
  Fixing this issue prevents sending broken packets to the decoder. With
  
  FFmpeg hevc decoder the frames are skipped, with VideoToolbox the frames
  
  are glitching.
  

  • [DH] libavformat/isom.h
  • [DH] libavformat/mov.c

• ffmpeg program written in C, cannot open my camera in macOS Catalina 10.15.7

  27 mai 2022, par marco0631

  #include 
#include 
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
#include "libavdevice/avdevice.h"

AVFormatContext* openCamera(void) {
    avdevice_register_all();
    AVFormatContext *ctx = avformat_alloc_context();
    AVInputFormat *ifmt = av_find_input_format("avfoundation");
    if (ifmt != NULL) {
        AVDictionary *opts = NULL;
        av_dict_set(&opts, "video_size", "1280x720", 0);
        av_dict_set(&opts, "framerate", "30", 0);
        av_dict_set(&opts, "pixel_format", "uyvy422", 0);
        
        int ret = avformat_open_input(&ctx, "0", ifmt, &opts);
        if (ret != 0) {
            printf("no");
            avformat_free_context(ctx);
            return NULL;
        }
    }
    return ctx;
}

int main(int argc, const char *argv[]) {
    openCamera();
}



  


  My code run on Xcode. After I have added the plist file, the running program camera opens for about half a second and then closes. and console output

  


  2022-02-22 00:39:19.372178&#x2B;0800 ffmpeg-tool[5977:195724] [plugin] AddInstanceForFactory: No factory registered for id <cfuuid 0x10640cf60="0x10640cf60"> F8BB1C28-BAE8-11D6-9C31-00039315CD46&#xA;2022-02-22 00:39:19.434783&#x2B;0800 ffmpeg-tool[5977:195724]  HALC_ShellDriverPlugIn::Open: Can&#x27;t get a pointer to the Open routine&#xA;2022-02-22 00:39:19.435262&#x2B;0800 ffmpeg-tool[5977:195724]  HALC_ShellDriverPlugIn::Open: Can&#x27;t get a pointer to the Open routine&#xA;2022-02-22 00:39:19.501780&#x2B;0800 ffmpeg-tool[5977:195724] [plugin] AddInstanceForFactory: No factory registered for id <cfuuid 0x10640f860="0x10640f860"> 30010C1C-93BF-11D8-8B5B-000A95AF9C6A&#xA;2022-02-22 00:39:19.605797&#x2B;0800 ffmpeg-tool[5977:195724] Metal API Validation Enabled&#xA;2022-02-22 00:39:21.701071&#x2B;0800 ffmpeg-tool[5977:195724] [] CMIOHardware.cpp:917:CMIODeviceStopStream the System is exiting&#xA;2022-02-22 00:39:21.701268&#x2B;0800 ffmpeg-tool[5977:195724] [] CMIOHardware.cpp:1332:CMIOStreamCopyBufferQueue the System is exiting&#xA;2022-02-22 00:39:21.701538&#x2B;0800 ffmpeg-tool[5977:195724] [] CMIOHardware.cpp:333:CMIOObjectGetPropertyData the System is exiting&#xA;2022-02-22 00:39:21.701767&#x2B;0800 ffmpeg-tool[5977:195724] [] CMIO_DALA_System.cpp:264:GetPropertyData error 1970171760 (unop) getting property selector (inot) scope (glob) element 0&#xA;2022-02-22 00:39:21.702472&#x2B;0800 ffmpeg-tool[5977:195724] [] CMIOHardware.cpp:333:CMIOObjectGetPropertyData the System is exiting&#xA;2022-02-22 00:39:21.702662&#x2B;0800 ffmpeg-tool[5977:195724] [] CMIO_DALA_System.cpp:264:GetPropertyData error 1970171760 (unop) getting property selector (inot) scope (glob) element 0&#xA;Program ended with exit code: 0&#xA;</cfuuid></cfuuid>

  


  How can I solve this problem ?

  


• Open Video Downloader Error : Postprocessing : ffmpeg not found

  11 septembre 2022, par Nick the Community Scientist

  Error Thrown :

  


  ERROR: Postprocessing: ffmpeg not found. Please install or provide the path using --ffmpeg-location


  


  Context : macOS Big Sur M1 Chip, using the open video downloader program GitHub release or Homebrew. This specifically was thrown at the end of downloading the video file and the audio file from a given URL. The two files remained separate as a result of the error, the video was playable normally, but audio was in a .webm format (unusable for most people).

  


  Analysis : It is clear that a dependency is missing, or its path cannot be located. For macOS users like me, the first step after checking the app's preferences for a path set or dependency download function is to check for the given dependency in the system. Once checking using Homebrew, it became clear that several dependencies were missing.