Recherche avancée

Sur d’autres sites (8166)

• C++/C FFmpeg artifact build up across video frames

  6 mars 2017, par ChiragRaman

  Context :
  I am building a recorder for capturing video and audio in separate threads (using Boost thread groups) using FFmpeg 2.8.6 on Ubuntu 16.04. I followed the demuxing_decoding example here : https://www.ffmpeg.org/doxygen/2.8/demuxing_decoding_8c-example.html

  Video capture specifics :
  I am reading H264 off a Logitech C920 webcam and writing the video to a raw file. The issue I notice with the video is that there seems to be a build-up of artifacts across frames until a particular frame resets. Here is my frame grabbing, and decoding functions :

  // Used for injecting decoding functions for different media types, allowing
  
  // for a generic decode loop
  
  typedef std::function PacketDecoder;
  
  
  
  /**
  
   * Decodes a video packet.
  
   * If the decoding operation is successful, returns the number of bytes decoded,
  
   * else returns the result of the decoding process from ffmpeg
  
   */
  
  int decode_video_packet(AVPacket *packet,
  
                          int *got_frame,
  
                          int cached){
  
      int ret = 0;
  
      int decoded = packet->size;
  
  
  
      *got_frame = 0;
  
  
  
      //Decode video frame
  
      ret = avcodec_decode_video2(video_decode_context,
  
                                  video_frame, got_frame, packet);
  
      if (ret < 0) {
  
          //FFmpeg users should use av_err2str
  
          char errbuf[128];
  
          av_strerror(ret, errbuf, sizeof(errbuf));
  
          std::cerr << "Error decoding video frame " << errbuf << std::endl;
  
          decoded = ret;
  
      } else {
  
          if (*got_frame) {
  
              video_frame->pts = av_frame_get_best_effort_timestamp(video_frame);
  
  
  
              //Write to log file
  
              AVRational *time_base = &video_decode_context->time_base;
  
              log_frame(video_frame, time_base,
  
                        video_frame->coded_picture_number, video_log_stream);
  
  
  
  #if( DEBUG )
  
              std::cout << "Video frame " << ( cached ? "(cached)" : "" )
  
                        << " coded:" <<  video_frame->coded_picture_number
  
                        << " pts:" << pts << std::endl;
  
  #endif
  
  
  
              /*Copy decoded frame to destination buffer:
  
               *This is required since rawvideo expects non aligned data*/
  
              av_image_copy(video_dest_attr.video_destination_data,
  
                            video_dest_attr.video_destination_linesize,
  
                            (const uint8_t **)(video_frame->data),
  
                            video_frame->linesize,
  
                            video_decode_context->pix_fmt,
  
                            video_decode_context->width,
  
                            video_decode_context->height);
  
  
  
              //Write to rawvideo file
  
              fwrite(video_dest_attr.video_destination_data[0],
  
                     1,
  
                     video_dest_attr.video_destination_bufsize,
  
                     video_out_file);
  
  
  
              //Unref the refcounted frame
  
              av_frame_unref(video_frame);
  
          }
  
      }
  
  
  
      return decoded;
  
  }
  
  
  
  /**
  
   * Grabs frames in a loop and decodes them using the specified decoding function
  
   */
  
  int process_frames(AVFormatContext *context,
  
                     PacketDecoder packet_decoder) {
  
      int ret = 0;
  
      int got_frame;
  
      AVPacket packet;
  
  
  
      //Initialize packet, set data to NULL, let the demuxer fill it
  
      av_init_packet(&packet);
  
      packet.data = NULL;
  
      packet.size = 0;
  
  
  
      // read frames from the file
  
      for (;;) {
  
          ret = av_read_frame(context, &packet);
  
          if (ret < 0) {
  
              if  (ret == AVERROR(EAGAIN)) {
  
                  continue;
  
              } else {
  
                  break;
  
              }
  
          }
  
  
  
          //Convert timing fields to the decoder timebase
  
          unsigned int stream_index = packet.stream_index;
  
          av_packet_rescale_ts(&packet,
  
                               context->streams[stream_index]->time_base,
  
                               context->streams[stream_index]->codec->time_base);
  
  
  
          AVPacket orig_packet = packet;
  
          do {
  
              ret = packet_decoder(&packet, &got_frame, 0);
  
              if (ret < 0) {
  
                  break;
  
              }
  
              packet.data += ret;
  
              packet.size -= ret;
  
          } while (packet.size > 0);
  
          av_free_packet(&orig_packet);
  
  
  
          if(stop_recording == true) {
  
              break;
  
          }
  
      }
  
  
  
      //Flush cached frames
  
      std::cout << "Flushing frames" << std::endl;
  
      packet.data = NULL;
  
      packet.size = 0;
  
      do {
  
          packet_decoder(&packet, &got_frame, 1);
  
      } while (got_frame);
  
  
  
      av_log(0, AV_LOG_INFO, "Done processing frames\n");
  
      return ret;
  
  }

  Questions :
  

  1. How do I go about debugging the underlying issue ?
     
  2. Is it possible that running the decoding code in a thread other than the one in which the decoding context was opened is causing the problem ?
     
  3. Am I doing something wrong in the decoding code ?

  Things I have tried/found :
  

  1. I found this thread that is about the same problem here : FFMPEG decoding artifacts between keyframes
     (I cannot post samples of my corrupted frames due to privacy issues, but the image linked to in that question depicts the same issue I have)
     However, the answer to the question is posted by the OP without specific details about how the issue was fixed. The OP only mentions that he wasn’t ’preserving the packets correctly’, but nothing about what was wrong or how to fix it. I do not have enough reputation to post a comment seeking clarification.

  2. I was initially passing the packet into the decoding function by value, but switched to passing by pointer on the off chance that the packet freeing was being done incorrectly.

  3. I found another question about debugging decoding issues, but couldn’t find anything conclusive : How is video decoding corruption debugged ?

  I’d appreciate any insight. Thanks a lot !

  [EDIT] In response to Ronald’s answer, I am adding a little more information that wouldn’t fit in a comment :

  1. I am only calling decode_video_packet() from the thread processing video frames ; the other thread processing audio frames calls a similar decode_audio_packet() function. So only one thread calls the function. I should mention that I have set the thread_count in the decoding context to 1, failing which I would get a segfault in malloc.c while flushing the cached frames.

  2. I can see this being a problem if the process_frames and the frame decoder function were run on separate threads, which is not the case. Is there a specific reason why it would matter if the freeing is done within the function, or after it returns ? I believe the freeing function is passed a copy of the original packet because multiple decode calls would be required for audio packet in case the decoder doesnt decode the entire audio packet.

  3. A general problem is that the corruption does not occur all the time. I can debug better if it is deterministic. Otherwise, I can’t even say if a solution works or not.

• Writing multithreaded video and audio packets with FFmpeg

  27 février 2017, par Robert Jones

  I couldn’t find any information on the way av_interleaved_write_frame deals with video and audio packets.

  I have multiple audio and video packets coming from 2 threads. Each thread calls a write_video_frame or write_audio_frame, locks a mutex, initialize an AVPacket and writes data to an .avi file.

  Initialization of AVCodecContext and AVFOrmatContext is ok.

  — Edit 1 —

  Audio and video are coming from an external source (microphone and camera) and are captured as raw data without any compression (even for video).
  I use h264 to encode video and no compression for Audio (PCM).

  Audio captured is : 16bits, 44100khz, stereo

  Video captured is 25FPS

  Question :

  1) Is it a problem if I write multiple video packets at once (let’s say 25 packets/sec) and just one audio packet/sec.

  Answer : Apparently not, the function av_interleaved_write_frame should be able to manage that kind of data as soon as pts and dts is well managed

  This means I call av_interleaved_write_frame 25 times for video writing and just 1 for audio writing per second. Could this be a problem ? If it is how can I deal with this scenario ?

  2) How can I manage pts and dts in this case ? It seems to be a problem in my application since I cannot correctly render the .avi file. Can I use real time stamps for both video and audio ?

  Answer : The best thing to do here is to use the timestamp given when capturing audio / video as pts and dts for this kind of application. So these are not exactly real time stamps (from wall clock) but media capture timestamps.

  Thank you for your precious advices.

• Libavformat/FFMPEG : Muxing into mp4 with AVFormatContext drops the final frame, depending on the number of frames

  27 octobre 2020, par Galen Lynch

  I am trying to use libavformat to create a .mp4 video
with a single h.264 video stream, but the final frame in the resulting file
often has a duration of zero and is effectively dropped from the video.
Strangely enough, whether the final frame is dropped or not depends on how many
frames I try to add to the file. Some simple testing that I outline below makes
me think that I am somehow misconfiguring either the AVFormatContext or the
h.264 encoder, resulting in two edit lists that sometimes chop off the final
frame. I will also post a simplified version of the code I am using, in case I'm
making some obvious mistake. Any help would be greatly appreciated : I've been
struggling with this issue for the past few days and have made little progress.

  


  I can recover the dropped frame by creating a new mp4 container using ffmpeg
binary with the copy codec if I use the -ignore_editlist option. Inspecting
the file with a missing frame using ffprobe, mp4trackdump, or mp4file --dump, shows that the final frame is dropped if its sample time is exactly the
same the end of the edit list. When I make a file that has no dropped frames, it
still has two edit lists : the only difference is that the end time of the edit
list is beyond all samples in files that do not have dropped frames. Though this
is hardly a fair comparison, if I make a .png for each frame and then generate
a .mp4 with ffmpeg using the image2 codec and similar h.264 settings, I
produce a movie with all frames present, only one edit list, and similar PTS
times as my mangled movies with two edit lists. In this case, the edit list
always ends after the last frame/sample time.

  


  I am using this command to determine the number of frames in the resulting stream,
though I also get the same number with other utilities :

  


  ffprobe -v error -count_frames -select_streams v:0 -show_entries stream=nb_read_frames -of default=nokey=1:noprint_wrappers=1 video_file_name.mp4


  


  Simple inspection of the file with ffprobe shows no obviously alarming signs to
me, besides the framerate being affected by the missing frame (the target was
24) :

  


  $ ffprobe -hide_banner testing.mp4
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'testing.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.45.100
  Duration: 00:00:04.13, start: 0.041016, bitrate: 724 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 100x100, 722 kb/s, 24.24 fps, 24 tbr, 12288 tbn, 48 tbc (default)
    Metadata:
      handler_name    : VideoHandler


  


  The files that I generate programatically always have two edit lists, one of
which is very short. In files both with and without a missing frame, the
duration one of the frames is 0, while all the others have the same duration
(512). You can see this in the ffmpeg output for this file that I tried to put
100 frames into, though only 99 are visible despite the file containing all 100
samples.

  


  $ ffmpeg -hide_banner -y -v 9 -loglevel 99 -i testing.mp4  &#xA;...&#xA;<edited to="to" remove="remove" the="the" class="class" printing="printing">&#xA;type:&#x27;edts&#x27; parent:&#x27;trak&#x27; sz: 48 100 948&#xA;type:&#x27;elst&#x27; parent:&#x27;edts&#x27; sz: 40 8 40&#xA;track[0].edit_count = 2&#xA;duration=41 time=-1 rate=1.000000&#xA;duration=4125 time=0 rate=1.000000&#xA;type:&#x27;mdia&#x27; parent:&#x27;trak&#x27; sz: 808 148 948&#xA;type:&#x27;mdhd&#x27; parent:&#x27;mdia&#x27; sz: 32 8 800&#xA;type:&#x27;hdlr&#x27; parent:&#x27;mdia&#x27; sz: 45 40 800&#xA;ctype=[0][0][0][0]&#xA;stype=vide&#xA;type:&#x27;minf&#x27; parent:&#x27;mdia&#x27; sz: 723 85 800&#xA;type:&#x27;vmhd&#x27; parent:&#x27;minf&#x27; sz: 20 8 715&#xA;type:&#x27;dinf&#x27; parent:&#x27;minf&#x27; sz: 36 28 715&#xA;type:&#x27;dref&#x27; parent:&#x27;dinf&#x27; sz: 28 8 28&#xA;Unknown dref type 0x206c7275 size 12&#xA;type:&#x27;stbl&#x27; parent:&#x27;minf&#x27; sz: 659 64 715&#xA;type:&#x27;stsd&#x27; parent:&#x27;stbl&#x27; sz: 151 8 651&#xA;size=135 4CC=avc1 codec_type=0&#xA;type:&#x27;avcC&#x27; parent:&#x27;stsd&#x27; sz: 49 8 49&#xA;type:&#x27;stts&#x27; parent:&#x27;stbl&#x27; sz: 32 159 651&#xA;track[0].stts.entries = 2&#xA;sample_count=99, sample_duration=512&#xA;sample_count=1, sample_duration=0&#xA;...&#xA;AVIndex stream 0, sample 99, offset 5a0ed, dts 50688, size 3707, distance 0, keyframe 1&#xA;Processing st: 0, edit list 0 - media time: -1, duration: 504&#xA;Processing st: 0, edit list 1 - media time: 0, duration: 50688&#xA;type:&#x27;udta&#x27; parent:&#x27;moov&#x27; sz: 98 1072 1162&#xA;...&#xA;</edited>

  


  The last frame has zero duration :

  


  $ mp4trackdump -v testing.mp4
...
mp4file testing.mp4, track 1, samples 100, timescale 12288
sampleId      1, size  6943 duration      512 time        0 00:00:00.000 S
sampleId      2, size  3671 duration      512 time      512 00:00:00.041 S
...
sampleId     99, size  3687 duration      512 time    50176 00:00:04.083 S
sampleId    100, size  3707 duration        0 time    50688 00:00:04.125 S


  


  Non-mangled videos that I generate have similar structure, as you can see in
this video that had 99 input frames, all of which are visible in the output.
Even though the sample_duration is set to zero for one of the samples in the
stss box, it is not dropped from the frame count or when reading the frames back
in with ffmpeg.

  


  $ ffmpeg -hide_banner -y -v 9 -loglevel 99 -i testing_99.mp4  
...
type:'elst' parent:'edts' sz: 40 8 40
track[0].edit_count = 2
duration=41 time=-1 rate=1.000000
duration=4084 time=0 rate=1.000000
...
track[0].stts.entries = 2
sample_count=98, sample_duration=512
sample_count=1, sample_duration=0
...
AVIndex stream 0, sample 98, offset 5d599, dts 50176, size 3833, distance 0, keyframe 1
Processing st: 0, edit list 0 - media time: -1, duration: 504
Processing st: 0, edit list 1 - media time: 0, duration: 50184
...


  


  $ mp4trackdump -v testing_99.mp4
...
sampleId     98, size  3814 duration      512 time    49664 00:00:04.041 S
sampleId     99, size  3833 duration        0 time    50176 00:00:04.083 S


  


  One difference that jumps out to me is that the mangled file's second edit list
ends at time 50688, which coincides with the last sample, while the non-mangled
file's edit list ends at 50184, which is after the time of the last sample
at 50176. As I mentioned before, whether the last frame is clipped depends on
the number of frames I encode and mux into the container : 100 input frames
results in 1 dropped frame, 99 results in 0, 98 in 0, 97 in 1, etc...

  


  Here is the code that I used to generate these files, which is a MWE script
version of library functions that I am modifying. It is written in Julia,
which I do not think is important here, and calls the FFMPEG library version
4.3.1. It's more or less a direct translation from of the FFMPEG muxing
demo, although the codec
context here is created before the format context. I am presenting the code that
interacts with ffmpeg first, although it relies on some helper code that I will
put below.

  


  The helper code just makes it easier to work with nested C structs in Julia, and
allows . syntax in Julia to be used in place of C's arrow (->) operator for
field access of struct pointers. Libav structs such as AVFrame appear as a
thin wrapper type AVFramePtr, and similarly AVStream appears as
AVStreamPtr etc... These act like single or double pointers for the purposes
of function calls, depending on the function's type signature. Hopefully it will
be clear enough to understand if you are familiar with working with libav in C,
and I don't think looking at the helper code should be necessary if you don't
want to run the code.

  


  # Function to transfer array to AVPicture/AVFrame
function transfer_img_buf_to_frame!(frame, img)
    img_pointer = pointer(img)
    data_pointer = frame.data[1] # Base-1 indexing, get pointer to first data buffer in frame
    for h = 1:frame.height
        data_line_pointer = data_pointer + (h-1) * frame.linesize[1] # base-1 indexing
        img_line_pointer = img_pointer + (h-1) * frame.width
        unsafe_copyto!(data_line_pointer, img_line_pointer, frame.width) # base-1 indexing
    end
end

# Function to transfer AVFrame to AVCodecContext, and AVPacket to AVFormatContext
function encode_mux!(packet, format_context, frame, codec_context; flush = false)
    if flush
        fret = avcodec_send_frame(codec_context, C_NULL)
    else
        fret = avcodec_send_frame(codec_context, frame)
    end
    if fret < 0 && !in(fret, [-Libc.EAGAIN, VIO_AVERROR_EOF])
        error("Error $fret sending a frame for encoding")
    end

    pret = Cint(0)
    while pret >= 0
        pret = avcodec_receive_packet(codec_context, packet)
        if pret == -Libc.EAGAIN || pret == VIO_AVERROR_EOF
             break
        elseif pret < 0
            error("Error $pret during encoding")
        end
        stream = format_context.streams[1] # Base-1 indexing
        av_packet_rescale_ts(packet, codec_context.time_base, stream.time_base)
        packet.stream_index = 0
        ret = av_interleaved_write_frame(format_context, packet)
        ret < 0 && error("Error muxing packet: $ret")
    end
    if !flush && fret == -Libc.EAGAIN && pret != VIO_AVERROR_EOF
        fret = avcodec_send_frame(codec_context, frame)
        if fret < 0 && fret != VIO_AVERROR_EOF
            error("Error $fret sending a frame for encoding")
        end
    end
    return pret
end

# Set parameters of test movie
nframe = 100
width, height = 100, 100
framerate = 24
gop = 0
codec_name = "libx264"
filename = "testing.mp4"

((width % 2 !=0) || (height % 2 !=0)) && error("Encoding error: Image dims must be a multiple of two")

# Make test images
imgstack = map(x->rand(UInt8,width,height),1:nframe);

pix_fmt = AV_PIX_FMT_GRAY8
framerate_rat = Rational(framerate)

codec = avcodec_find_encoder_by_name(codec_name)
codec == C_NULL && error("Codec '$codec_name' not found")

# Allocate AVCodecContext
codec_context_p = avcodec_alloc_context3(codec) # raw pointer
codec_context_p == C_NULL && error("Could not allocate AVCodecContext")
# Easier to work with pointer that acts like a c struct pointer, type defined below
codec_context = AVCodecContextPtr(codec_context_p)

codec_context.width = width
codec_context.height = height
codec_context.time_base = AVRational(1/framerate_rat)
codec_context.framerate = AVRational(framerate_rat)
codec_context.pix_fmt = pix_fmt
codec_context.gop_size = gop

ret = avcodec_open2(codec_context, codec, C_NULL)
ret < 0 && error("Could not open codec: Return code $(ret)")

# Allocate AVFrame and wrap it in a Julia convenience type
frame_p = av_frame_alloc()
frame_p == C_NULL && error("Could not allocate AVFrame")
frame = AVFramePtr(frame_p)

frame.format = pix_fmt
frame.width = width
frame.height = height

# Allocate picture buffers for frame
ret = av_frame_get_buffer(frame, 0)
ret < 0 && error("Could not allocate the video frame data")

# Allocate AVPacket and wrap it in a Julia convenience type
packet_p = av_packet_alloc()
packet_p == C_NULL && error("Could not allocate AVPacket")
packet = AVPacketPtr(packet_p)

# Allocate AVFormatContext and wrap it in a Julia convenience type
format_context_dp = Ref(Ptr{AVFormatContext}()) # double pointer
ret = avformat_alloc_output_context2(format_context_dp, C_NULL, C_NULL, filename)
if ret != 0 || format_context_dp[] == C_NULL
    error("Could not allocate AVFormatContext")
end
format_context = AVFormatContextPtr(format_context_dp)

# Add video stream to AVFormatContext and configure it to use the encoder made above
stream_p = avformat_new_stream(format_context, C_NULL)
stream_p == C_NULL && error("Could not allocate output stream")
stream = AVStreamPtr(stream_p) # Wrap this pointer in a convenience type

stream.time_base = codec_context.time_base
stream.avg_frame_rate = 1 / convert(Rational, stream.time_base)
ret = avcodec_parameters_from_context(stream.codecpar, codec_context)
ret < 0 && error("Could not set parameters of stream")

# Open the AVIOContext
pb_ptr = field_ptr(format_context, :pb)
# This following is just a call to avio_open, with a bit of extra protection
# so the Julia garbage collector does not destroy format_context during the call
ret = GC.@preserve format_context avio_open(pb_ptr, filename, AVIO_FLAG_WRITE)
ret < 0 && error("Could not open file $filename for writing")

# Write the header
ret = avformat_write_header(format_context, C_NULL)
ret < 0 && error("Could not write header")

# Encode and mux each frame
for i in 1:nframe # iterate from 1 to nframe
    img = imgstack[i] # base-1 indexing
    ret = av_frame_make_writable(frame)
    ret < 0 && error("Could not make frame writable")
    transfer_img_buf_to_frame!(frame, img)
    frame.pts = i
    encode_mux!(packet, format_context, frame, codec_context)
end

# Flush the encoder
encode_mux!(packet, format_context, frame, codec_context; flush = true)

# Write the trailer
av_write_trailer(format_context)

# Close the AVIOContext
pb_ptr = field_ptr(format_context, :pb) # get pointer to format_context.pb
ret = GC.@preserve format_context avio_closep(pb_ptr) # simply a call to avio_closep
ret < 0 && error("Could not free AVIOContext")

# Deallocation
avcodec_free_context(codec_context)
av_frame_free(frame)
av_packet_free(packet)
avformat_free_context(format_context)


  


  Below is the helper code that makes accessing pointers to nested c structs not a
total pain in Julia. If you try to run the code yourself, please enter this in
before the logic of the code shown above. It requires
VideoIO.jl, a Julia wrapper to libav.

  


  # Convenience type and methods to make the above code look more like C
using Base: RefValue, fieldindex

import Base: unsafe_convert, getproperty, setproperty!, getindex, setindex!,
    unsafe_wrap, propertynames

# VideoIO is a Julia wrapper to libav
#
# Bring bindings to libav library functions into namespace
using VideoIO: AVCodecContext, AVFrame, AVPacket, AVFormatContext, AVRational,
    AVStream, AV_PIX_FMT_GRAY8, AVIO_FLAG_WRITE, AVFMT_NOFILE,
    avformat_alloc_output_context2, avformat_free_context, avformat_new_stream,
    av_dump_format, avio_open, avformat_write_header,
    avcodec_parameters_from_context, av_frame_make_writable, avcodec_send_frame,
    avcodec_receive_packet, av_packet_rescale_ts, av_interleaved_write_frame,
    avformat_query_codec, avcodec_find_encoder_by_name, avcodec_alloc_context3,
    avcodec_open2, av_frame_alloc, av_frame_get_buffer, av_packet_alloc,
    avio_closep, av_write_trailer, avcodec_free_context, av_frame_free,
    av_packet_free

# Submodule of VideoIO
using VideoIO: AVCodecs

# Need to import this function from Julia's Base to add more methods
import Base: convert

const VIO_AVERROR_EOF = -541478725 # AVERROR_EOF

# Methods to convert between AVRational and Julia's Rational type, because it's
# hard to access the AV rational macros with Julia's C interface
convert(::Type{Rational{T}}, r::AVRational) where T = Rational{T}(r.num, r.den)
convert(::Type{Rational}, r::AVRational) = Rational(r.num, r.den)
convert(::Type{AVRational}, r::Rational) = AVRational(numerator(r), denominator(r))

"""
    mutable struct NestedCStruct{T}

Wraps a pointer to a C struct, and acts like a double pointer to that memory.
The methods below will automatically convert it to a single pointer if needed
for a function call, and make interacting with it in Julia look (more) similar
to interacting with it in C, except '->' in C is replaced by '.' in Julia.
"""
mutable struct NestedCStruct{T}
    data::RefValue{Ptr{T}}
end
NestedCStruct{T}(a::Ptr) where T = NestedCStruct{T}(Ref(a))
NestedCStruct(a::Ptr{T}) where T = NestedCStruct{T}(a)

const AVCodecContextPtr = NestedCStruct{AVCodecContext}
const AVFramePtr = NestedCStruct{AVFrame}
const AVPacketPtr = NestedCStruct{AVPacket}
const AVFormatContextPtr = NestedCStruct{AVFormatContext}
const AVStreamPtr = NestedCStruct{AVStream}

function field_ptr(::Type{S}, struct_pointer::Ptr{T}, field::Symbol,
                           index::Integer = 1) where {S,T}
    fieldpos = fieldindex(T, field)
    field_pointer = convert(Ptr{S}, struct_pointer) +
        fieldoffset(T, fieldpos) + (index - 1) * sizeof(S)
    return field_pointer
end

field_ptr(a::Ptr{T}, field::Symbol, args...) where T =
    field_ptr(fieldtype(T, field), a, field, args...)

function check_ptr_valid(p::Ptr, err::Bool = true)
    valid = p != C_NULL
    err && !valid && error("Invalid pointer")
    valid
end

unsafe_convert(::Type{Ptr{T}}, ap::NestedCStruct{T}) where T =
    getfield(ap, :data)[]
unsafe_convert(::Type{Ptr{Ptr{T}}}, ap::NestedCStruct{T}) where T =
    unsafe_convert(Ptr{Ptr{T}}, getfield(ap, :data))

function check_ptr_valid(a::NestedCStruct{T}, args...) where T
    p = unsafe_convert(Ptr{T}, a)
    GC.@preserve a check_ptr_valid(p, args...)
end

nested_wrap(x::Ptr{T}) where T = NestedCStruct(x)
nested_wrap(x) = x

function getproperty(ap::NestedCStruct{T}, s::Symbol) where T
    check_ptr_valid(ap)
    p = unsafe_convert(Ptr{T}, ap)
    res = GC.@preserve ap unsafe_load(field_ptr(p, s))
    nested_wrap(res)
end

function setproperty!(ap::NestedCStruct{T}, s::Symbol, x) where T
    check_ptr_valid(ap)
    p = unsafe_convert(Ptr{T}, ap)
    fp = field_ptr(p, s)
    GC.@preserve ap unsafe_store!(fp, x)
end

function getindex(ap::NestedCStruct{T}, i::Integer) where T
    check_ptr_valid(ap)
    p = unsafe_convert(Ptr{T}, ap)
    res = GC.@preserve ap unsafe_load(p, i)
    nested_wrap(res)
end

function setindex!(ap::NestedCStruct{T}, i::Integer, x) where T
    check_ptr_valid(ap)
    p = unsafe_convert(Ptr{T}, ap)
    GC.@preserve ap unsafe_store!(p, x, i)
end

function unsafe_wrap(::Type{T}, ap::NestedCStruct{S}, i) where {S, T}
    check_ptr_valid(ap)
    p = unsafe_convert(Ptr{S}, ap)
    GC.@preserve ap unsafe_wrap(T, p, i)
end

function field_ptr(::Type{S}, a::NestedCStruct{T}, field::Symbol,
                           args...) where {S, T}
    check_ptr_valid(a)
    p = unsafe_convert(Ptr{T}, a)
    GC.@preserve a field_ptr(S, p, field, args...)
end

field_ptr(a::NestedCStruct{T}, field::Symbol, args...) where T =
    field_ptr(fieldtype(T, field), a, field, args...)

propertynames(ap::T) where {S, T<:NestedCStruct{S}} = (fieldnames(S)...,
                                                       fieldnames(T)...)


  


  ---

  


  Edit : Some things that I have already tried

  


  

  • Explicitly setting the stream duration to be the same number as the number of frames that I add, or a few more beyond that

  


  • Explicitly setting the stream start time to zero, while the first frame has a PTS of 1

  


  • Playing around with encoder parameters, as well as gop_size, using B frames, etc.

  


  • Setting the private data for the mov/mp4 muxer to set the movflag negative_cts_offsets

  


  • Changing the framerate

  


  • Tried different pixel formats, such as AV_PIX_FMT_YUV420P

  


  


  Also to be clear while I can just transfer the file into another while ignoring the edit lists to work around this problem, I am hoping to not make damaged mp4 files in the first place.