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• Muxing with libav

  14 février 2014, par LordDoskias

  I have a program which is supposed to demux input mpeg-ts, transcode the mpeg2 into h264 and then mux the audio alongside the transcoded video. When I open the resulting muxed file with VLC I neither get audio nor video. Here is the relevant code.

  My main worker loop is as follows :

  void
  
  *writer_thread(void *thread_ctx) {
  
  
  
      struct transcoder_ctx_t *ctx = (struct transcoder_ctx_t *) thread_ctx;
  
      AVStream *video_stream = NULL, *audio_stream = NULL;
  
      AVFormatContext *output_context = init_output_context(ctx, &video_stream, &audio_stream);
  
      struct mux_state_t mux_state = {0};
  
  
  
      //from omxtx
  
      mux_state.pts_offset = av_rescale_q(ctx->input_context->start_time, AV_TIME_BASE_Q, output_context->streams[ctx->video_stream_index]->time_base);
  
  
  
      //write stream header if any
  
      avformat_write_header(output_context, NULL);
  
  
  
      //do not start doing anything until we get an encoded packet
  
      pthread_mutex_lock(&ctx->pipeline.video_encode.is_running_mutex);
  
      while (!ctx->pipeline.video_encode.is_running) {
  
          pthread_cond_wait(&ctx->pipeline.video_encode.is_running_cv, &ctx->pipeline.video_encode.is_running_mutex);
  
      }
  
  
  
      while (!ctx->pipeline.video_encode.eos || !ctx->processed_audio_queue->queue_finished) {
  
          //FIXME a memory barrier is required here so that we don't race 
  
          //on above variables 
  
  
  
          //fill a buffer with video data 
  
          OERR(OMX_FillThisBuffer(ctx->pipeline.video_encode.h, omx_get_next_output_buffer(&ctx->pipeline.video_encode)));
  
  
  
          write_audio_frame(output_context, audio_stream, ctx); //write full audio frame 
  
          //FIXME no guarantee that we have a full frame per packet?
  
          write_video_frame(output_context, video_stream, ctx, &mux_state); //write full video frame
  
          //encoded_video_queue is being filled by the previous command
  
  
  
      }
  
  
  
      av_write_trailer(output_context);
  
  
  
      //free all the resources
  
      avcodec_close(video_stream->codec);
  
      avcodec_close(audio_stream->codec);
  
      /* Free the streams. */
  
      for (int i = 0; i < output_context->nb_streams; i++) {
  
          av_freep(&output_context->streams[i]->codec);
  
          av_freep(&output_context->streams[i]);
  
      }
  
  
  
      if (!(output_context->oformat->flags & AVFMT_NOFILE)) {
  
          /* Close the output file. */
  
          avio_close(output_context->pb);
  
      }
  
  
  
  
  
      /* free the stream */
  
      av_free(output_context);
  
      free(mux_state.pps);
  
      free(mux_state.sps);
  
  }

  The code for initialising libav output context is this :

  static 
  
  AVFormatContext *
  
  init_output_context(const struct transcoder_ctx_t *ctx, AVStream **video_stream, AVStream **audio_stream) {
  
      AVFormatContext *oc;
  
      AVOutputFormat *fmt;
  
      AVStream *input_stream, *output_stream;
  
      AVCodec *c;
  
      AVCodecContext *cc;
  
      int audio_copied = 0; //copy just 1 stream
  
  
  
      fmt = av_guess_format("mpegts", NULL, NULL);
  
      if (!fmt) {
  
          fprintf(stderr, "[DEBUG] Error guessing format, dying\n");
  
          exit(199);
  
      }
  
  
  
      oc = avformat_alloc_context();
  
      if (!oc) {
  
          fprintf(stderr, "[DEBUG] Error allocating context, dying\n");
  
          exit(200);
  
      }
  
  
  
      oc->oformat = fmt;
  
      snprintf(oc->filename, sizeof(oc->filename), "%s", ctx->output_filename);
  
      oc->debug = 1;
  
      oc->start_time_realtime = ctx->input_context->start_time;
  
      oc->start_time = ctx->input_context->start_time;
  
      oc->duration = 0;
  
      oc->bit_rate = 0;
  
  
  
      for (int i = 0; i < ctx->input_context->nb_streams; i++) {
  
          input_stream = ctx->input_context->streams[i];
  
          output_stream = NULL;
  
          if (input_stream->index == ctx->video_stream_index) {
  
              //copy stuff from input video index
  
              c = avcodec_find_encoder(CODEC_ID_H264);
  
              output_stream = avformat_new_stream(oc, c);
  
              *video_stream = output_stream;
  
              cc = output_stream->codec;
  
              cc->width = input_stream->codec->width;
  
              cc->height = input_stream->codec->height;
  
              cc->codec_id = CODEC_ID_H264;
  
              cc->codec_type = AVMEDIA_TYPE_VIDEO;
  
              cc->bit_rate = ENCODED_BITRATE;
  
              cc->time_base = input_stream->codec->time_base;
  
  
  
              output_stream->avg_frame_rate = input_stream->avg_frame_rate;
  
              output_stream->r_frame_rate = input_stream->r_frame_rate;
  
              output_stream->start_time = AV_NOPTS_VALUE;
  
  
  
          } else if ((input_stream->codec->codec_type == AVMEDIA_TYPE_AUDIO) && !audio_copied)  { 
  
              /* i care only about audio */
  
              c = avcodec_find_encoder(input_stream->codec->codec_id);
  
              output_stream = avformat_new_stream(oc, c);
  
              *audio_stream = output_stream;
  
              avcodec_copy_context(output_stream->codec, input_stream->codec);
  
              /* Apparently fixes a crash on .mkvs with attachments: */
  
              av_dict_copy(&output_stream->metadata, input_stream->metadata, 0);
  
              /* Reset the codec tag so as not to cause problems with output format */
  
              output_stream->codec->codec_tag = 0;
  
              audio_copied = 1;
  
          }
  
      }
  
  
  
      for (int i = 0; i < oc->nb_streams; i++) {
  
          if (oc->oformat->flags & AVFMT_GLOBALHEADER)
  
              oc->streams[i]->codec->flags |= CODEC_FLAG_GLOBAL_HEADER;
  
          if (oc->streams[i]->codec->sample_rate == 0)
  
              oc->streams[i]->codec->sample_rate = 48000; /* ish */
  
      }
  
  
  
      if (!(fmt->flags & AVFMT_NOFILE)) {
  
          fprintf(stderr, "[DEBUG] AVFMT_NOFILE set, allocating output container\n");
  
          if (avio_open(&oc->pb, ctx->output_filename, AVIO_FLAG_WRITE) < 0) {
  
              fprintf(stderr, "[DEBUG] error creating the output context\n");
  
              exit(1);
  
          }
  
      }
  
  
  
      return oc;
  
  }

  Finally this is the code for writing audio :

  static
  
  void
  
  write_audio_frame(AVFormatContext *oc, AVStream *st, struct transcoder_ctx_t *ctx) {
  
      AVPacket pkt = {0}; // data and size must be 0;
  
      struct packet_t *source_audio;
  
      av_init_packet(&pkt);
  
  
  
      if (!(source_audio = packet_queue_get_next_item_asynch(ctx->processed_audio_queue))) {
  
          return;
  
      }
  
  
  
      pkt.stream_index = st->index;
  
      pkt.size = source_audio->data_length;
  
      pkt.data = source_audio->data;
  
      pkt.pts = source_audio->PTS;
  
      pkt.dts = source_audio->DTS;
  
      pkt.duration = source_audio->duration;
  
      pkt.destruct = avpacket_destruct;
  
      /* Write the compressed frame to the media file. */
  
      if (av_interleaved_write_frame(oc, &pkt) != 0) {
  
          fprintf(stderr, "[DEBUG] Error while writing audio frame\n");
  
      }
  
  
  
      packet_queue_free_packet(source_audio, 0);
  
  }

  A resulting mpeg4 file can be obtained from here : http://87.120.131.41/dl/mpeg4.h264

  I have ommited the write_video_frame code since it is a lot more complicated and I might be making something wrong there as I'm doing timebase conversation etc. For audio however I'm doing 1:1 copy. Each packet_t packet contains data from av_read_frame from the input mpegts container. In the worst case I'd expect that my audio is working and not my video. However I cannot get either of those to work. Seems the documentation is rather vague on making things like that - I've tried both libav and ffmpeg irc channels to no avail. Any information regarding how I can debug the issue will be greatly appreciated.

• Exit Status with ffmpeg Command in Rails

  25 novembre 2012, par DragonFire353

  I am trying to get uploaded videos to be converted in the background, running windows. I am using :

  gem 'paperclip'
  
  gem 'aasm'
  
  gem 'delayed_job_active_record'
  
  gem 'ffmpeg'

  I was using purely paperclip before and making the user wait and it worked great, now I am having problems with the return of the error status for the command, I have tried editing to possible fix the command wondering if it was failing in the first place but I keep getting :

  undefined method `exitstatus' for nil:NilClass

  no matter what. I've tried looking this up and it's supposedly valid syntax that should work... Also I've commented out the actual spawn do part because I get another error if I leave that in :

  wrong number of arguments

  Does anyone know how to properly get this working ? I've went through a few tutorials that have bits and pieces of what I need but I can't get them working together. Here's what I have so far, lemme know if you need more :

  Model :

      class Video < ActiveRecord::Base
  
    include AASM
  
  
  
    belongs_to :user
  
    has_many :comments, dependent: :destroy
  
    attr_accessible :video, :user_id, :video_file_name, :title, :public, :description, :views
  
  
  
    has_attached_file :video, url: "/users/:user_id/videos/:id/:basename_:style.:extension"
  
    #, :styles => { 
  
       # :video => { geometry: "800x480>", format: 'webm' },
  
       # :thumb => { geometry: "200x200>", format: 'png', time: 3 },
  
     # }, processors: [:ffmpeg], url: "/users/:user_id/videos/:id/:basename_:style.:extension"
  
  
  
    #process_in_background :video #causes death
  
  
  
    validates :video, presence: true
  
    validates :description, presence: true, length: { minimum: 5, maximum: 100}
  
    validates :title, presence: true, length: { minimum: 1, maximum: 15 }
  
  
  
    validates_attachment_size :video, less_than: 1.gigabytes
  
    validates_attachment :video, presence: true
  
  
  
    default_scope order: 'created_at DESC'
  
  
  
    Paperclip.interpolates :user_id do |attachment, style|attachment.instance.user_id
  
    end
  
  
  
    #acts as state machine plugin
  
    aasm state: :pending do
  
     state :pending, initial: true
  
     state :converting
  
     state :converted
  
     #, enter: :set_new_filename
  
     state :error
  
  
  
      event :convert do
  
       transitions from: :pending, to: :converting
  
     end
  
  
  
      event :converted do
  
       transitions from: :converting, to: :converted
  
     end
  
  
  
      event :failure do
  
        transitions from: :converting, to: :error
  
      end
  
    end
  
  
  
     # This method is called from the controller and takes care of the converting
  
    def convert
  
      self.convert!
  
  
  
      #spawn a new thread to handle conversion
  
      #spawn do
  
        success = delay.system(convert_command)
  
        logger.debug 'Converting File: ' + success.to_s
  
        if success && $?.exitstatus.to_i == 0
  
          self.converted!
  
        else
  
          self.failure!
  
        end
  
      #end
  
    end
  
  
  
    def self.search(search)
  
      if search
  
        find(:all, conditions: ["public = 't' AND title LIKE ?", "%#{search}%"], order: "created_at DESC")
  
      else
  
        find(:all, conditions: ["public = 't'"], order: "created_at DESC")
  
      end
  
    end
  
  
  
    def self.admin_search(search)
  
      if search
  
        find(:all, conditions: ['title LIKE ?', "%#{search}%"], order: "created_at DESC")
  
      else
  
        find(:all, order: "created_at DESC")
  
      end
  
    end
  
  
  
    private
  
      def convert_command
  
        #construct new file extension
  
        webm =  "." + id.to_s + ".webm"
  
  
  
        #build the command to execute ffmpeg
  
        command = <<-end_command
  
          ffmpeg -i #{ RAILS_ROOT + '/public/users/:user_id/videos/:id/:basename_:style.:extension' }  -ar 22050 -ab 32 -s 1280x720 -vcodec webm -r 25 -qscale 8 -f webm -y #{ RAILS_ROOT + '/public/users/:user_id/videos/:id/:basename_.webm' }
  
  
  
        end_command
  
  
  
        logger.debug "Converting video...command: " + command
  
        command
  
      end
  
  
  
      handle_asynchronously :convert_command
  
  
  
      # This updates the stored filename with the new flash video file
  
      def set_new_filename
  
        #update_attribute(:filename, "#{filename}.#{id}.webm")
  
        update_attribute(:content_type, "video/x-webm")
  
      end
  
  
  
  end

  Controller :

  class VideosController < ApplicationController
  
  before_filter :signed_in_user, only: [:upload, :update, :destroy]
  
  before_filter :admin_user, only: :admin_index
  
  
  
  def upload
  
      @video = Video.new
  
      # generate a unique id for the upload
  
      @uuid = (0..29).to_a.map {|x| rand(10)}
  
  end
  
  
  
  def create
  
      @video = Video.new(params[:video])
  
      @video.user_id = current_user.id
  
  
  
      if @video.save
  
          @video.convert
  
          flash[:success] = "Uploaded Succefully!"
  
          redirect_to @video.user
  
      else
  
          render 'upload'
  
      end
  
  end
  
  
  
  def show
  
      @video = Video.find(params[:id])
  
      @comments = @video.comments.paginate(page: params[:page], per_page: 6)
  
      if !@video.public
  
          if !signed_in? || current_user.id != @video.user_id  && !current_user.admin && !current_user.approved?(@video.user)
  
          flash[:notice] = "Video is private"
  
          redirect_to root_path
  
      end
  
  end
  
  end
  
  
  
  def update
  
      @video = Video.find(params[:id])
  
      if @video.update_attributes(params[:video])
  
    flash[:success] = "Video preferences saved"
  
  else
  
      flash[:fail] = "Failed to update video preferences"
  
  end
  
  redirect_to :back
  
  end
  
  
  
  def destroy
  
      @video = Video.find(params[:id])
  
      @video.destroy
  
      flash[:deleted] = "Deleted Succefully!"
  
      redirect_to :back
  
  end
  
  
  
  def index
  
      @videos = Video.paginate(page: params[:page], per_page: 6).search(params[:search])
  
  end
  
  
  
  def admin_index
  
      @videos = Video.paginate(page: params[:page], per_page: 6).admin_search(params[:search])
  
  end
  
  
  
  def ajax_video_comments
  
      @video = Video.find(params[:id])
  
      @comments = @video.comments.paginate(page: params[:page], per_page: 6)
  
  
  
      respond_to do |format|
  
      format.js   { render partial: 'shared/comments', content_type: 'text/html' }
  
  end
  
  end
  
  
  
  def ajax_video_watched
  
      @video = Video.find(params[:id])
  
      @video.views += 1
  
      @video.save
  
  end
  
  
  
  private
  
  
  
  def signed_in_user
  
      redirect_to root_path, notice: "Please Login." unless signed_in?
  
  end
  
  
  
  def admin_user
  
      redirect_to(root_path) unless current_user.admin?
  
  end
  
  
  
  end

• Running Windows XP In 2016

  2 janvier 2016, par Multimedia Mike

  I have an interest in getting a 32-bit Windows XP machine up and running. I have a really good yet slightly dated and discarded computer that seemed like a good candidate for dedicating to this task. So the question is : Can Windows XP still be installed from scratch on a computer, activated, and used in 2016 ? I wasn’t quite sure since I have heard stories about how Microsoft has formally ended support for Windows XP as of the first half of 2014 and I wasn’t entirely sure what that meant.

  Spoiler : It’s still possible to install and activate Windows XP as of the writing of this post. It’s also possible to download and install all the updates published up until support ended.

  The Candidate Computer
  This computer was assembled either in late 2008 or early 2009. It was a beast at the time.

  
  
  Click for a larger image
  

  It was built around the newly-released NVIDIA GTX 280 video card. The case is a Thermaltake DH-101, which is a home theater PC thing. The motherboard is an Asus P5N32-SLI Premium with a Core 2 Duo X6800 2.93 GHz CPU on board. 2 GB of RAM and a 1.5 TB hard drive are also present.

  The original owner handed it off to me because their family didn’t have much use for it anymore (too many other machines in the house). Plus it was really, obnoxiously loud. The noisy culprit was the stock blue fan that came packaged with the Intel processor (seen in the photo) whining at around 65 dB. I replaced the fan and brought the noise level way down.

  As for connectivity, the motherboard has dual gigabit NICs (of 2 different chipsets for some reason) and onboard wireless 802.11g. I couldn’t make the latter work and this project was taking place a significant distance from my wired network. Instead, I connected a USB 802.11ac dongle and antenna which is advertised to work in both Windows XP and Linux. It works great under Windows XP. Meanwhile, making the adapter work under Linux provided a retro-computing adventure in which I had to modify C code to make the driver work.

  So, score 1 for Windows XP over Linux here.

  The Simple Joy of Retro-computing
  One thing you have to watch out for when you get into retro-computing is fighting the urge to rant about the good old days of computing. Most long-time computer users have a good understanding of the frustration that computers keep getting faster by orders of magnitude and yet using them somehow feels slower and slower over successive software generations.
  

  This really hits home when you get old software running, especially on high-end hardware (relative to what was standard contemporary hardware). After I got this new Windows XP machine running, as usual, I was left wondering why software was so much faster a few generations ago.

  Of course, as mentioned, it helps when you get to run old software on hardware that would have been unthinkably high end at the software’s release. Apparently, the minimum WinXP specs as set by MS are a 233 MHz Pentium CPU and 64 MB of RAM, with 1.5 GB of hard drive space. This machine has more than 10x the clock speed (and 2 CPUs), 32x the RAM, and 1000x the HD space. Further, I’m pretty sure 100 Mbit ethernet was the standard consumer gear in 2001 while 802.11b wireless was gaining traction. The 802.11ac adapter makes networking quite pleasant.

  Purpose
  Retro-computing really seems to be ramping up in popularity lately. For some reason, I feel compelled to declare at this juncture that I was into it before it was cool.

  Why am I doing this ? I have a huge collection of old DOS/Windows computer games. I also have this nerdy obsession with documenting old video games in the MobyGames database. I used to do a lot of this a few years ago, tracking the effort on my gaming blog. In the intervening years, I have still collected a lot of old, unused, unloved video games, usually either free or very cheap while documenting my collection efforts on that same blog.

  So I want to work my way through some of this backlog, particularly the games that are not yet represented in the MobyGames database, and even more pressing, ones that the internet (viewed through Google at least) does not seem to know about. To that end, I thought this was a good excuse to get Windows XP on this old machine. A 32-bit Windows XP machine is capable of running any software advertised as supporting Windows XP, Windows ME, Windows 98, Windows 95, and even 16-bit Windows 3.x (I have games for all these systems). That covers a significant chunk of PC history. It can probably be made to run DOS games as well, but those are (usually) better run under DosBox. In order to get the right display feel, I even invested in a (used) monitor sporting a 4:3 aspect ratio. If I know these old games, most will be engineered and optimized for that ratio rather than the widescreen resolutions seen nowadays.

  I would also like to get back to that Xbox optical disc experimentation I was working on a few years ago. Another nice feature of this motherboard is that it still provides a 40-pin IDE/PATA adapter which makes the machine useful for continuing that old investigation (and explains why I have that long IDE cable to no where pictured hanging off the board).

  The Messy Details
  I did the entire installation process twice. The first time was a bumbling journey of discovery and copious note-taking. I still have Windows XP installation media that includes service pack 2 (SP2), along with 2 separate licenses that haven’t been activated for a long time. My plan was to install it fresh, then install the relevant drivers. Then I would investigate the Windows update and activation issues and everything should be fine.

  So what’s the deal with Windows Update for XP, and with activations ? Second item first : it IS possible to still activate Windows XP. The servers are still alive and respond quickly. However, as always, you don’t activate until you’re sure everything is working at some baseline. It took awhile to get there.

  As for whether Windows Update still works for XP, that’s a tougher question. Short answer is yes ; longer answer is that it can be difficult to kick off the update process. At least on SP2, the “Windows Update” program launches IE6 and navigates to a special microsoft.com URL which initiates the update process (starting with an ActiveX control). This URL no longer exists.

  From what I can piece together from my notes, this seems to be the route I eventually took :

  1. Install Windows XP fresh
  2. Install drivers for the hardware ; fortunately, Asus still has all the latest drivers necessary for the motherboard and its components but it’s necessary to download these from another network-connected PC since the networking probably won’t be running “out of the box”
  3. Download the .NET 3.5 runtime, which is the last one supported by Windows XP, and install it
  4. Download the latest NVIDIA drivers ; this needs to be done after the previous step because the installer requires the .NET runtime ; run the driver installer and don’t try to understand why it insists on re-downloading .NET 3.5 runtime before installation
  5. While you’re downloading stuff on other computers to be transported to this new machine, be sure to download either Chrome or Firefox per your preference ; if you try to download via IE6, you may find that their download pages aren’t compatible with IE6
  6. Somewhere along the line (I’m guessing as a side effect of the .NET 3.5 installation), the proper, non-IE6-based Windows Update program magically springs to life ; once this happens, there will be 144 updates (in my case anyway) ; installing these will probably require multiple reboots, but SP3 and all known pre-deprecation security fixes will be installed
  7. Expect that, even after installing all of these, a few more updates will appear ; eventually, you’ll be at the end of the update road
  8. Once you’re satisfied everything is working satisfactorily, take the plunge and activate your installation

  Residual Quirks
  Steam runs great on Windows XP, as do numerous games I have purchased through the service. So that opens up a whole bunch more games that I could play on this machine. Steam’s installer highlights a curious legacy problem of Windows XP– it seems there are many languages that it does not support “out of the box” :

  
  
  

  It looks like the Chinese options and a few others that are standard now weren’t standard 15 years ago.

  Also, a little while after booting up, I’ll get a crashing error concerning a process called geoforms.scr. This appears to be NVIDIA-related. However, I don’t notice anything obviously operationally wrong with the system.

  Regarding DirectX support, DirectX 9 is the highest version officially supported by Windows XP. There are allegedly methods to get DirectX 10 running as well, but I don’t care that much. I did care, briefly, when I realized that a bunch of the demos for the NVIDIA GTX 280 required DX10 which left me wondering why it was possible to install them on Windows XP.

  Eventually, by installing enough of these old games, I fully expect to have numerous versions of .NET, DirectX, QT, and Video for Windows installed side by side.

  Out of curiosity, I tried playing a YouTube HD/1080p video. I wanted to see if the video was accelerated through my card. The video played at full speed but I noticed some tearing. Then I inspected the CPU usage and noticed that the CPU was quite loaded. So either the GTX 280 doesn’t have video acceleration, or Windows XP doesn’t provide the right APIs, or Chrome is not able to access the APIs in Windows XP, or perhaps some combination of the foregoing.

  Games are working well, though. I tried one of my favorite casual games and got sucked into that for, like, an entire night because that’s what casual games do. But then, I booted up a copy of WarCraft III that I procured sometime ago. I don’t have any experience with the WarCraft universe (RTS or MMO) but I developed a keen interest in StarCraft II over the past few years and wanted to try WarCraft III. Unfortunately, I couldn’t get WarCraft III to work correctly on several different Windows 7 installations (movies didn’t play, which left me slightly confused as to what I was supposed to do).

  Still works beautifully on the new old Windows XP machine.