Recherche avancée

Sur d’autres sites (11884)

• How to use FFMPEG API to decode to client allocated memory

  25 mars 2020, par VorpalSword

  I’m trying to use the FFMPEG API to decode into a buffer defined by the client program by following the tips in this question but using the new pattern for decoding instead of the now deprecated avcodec_decode_video2 function.

  If my input file is an I-frame only format, everything works great. I’ve tested with a .mov file encoded with v210 (uncompressed).

  However, if the input is a long-GoP format (I’m trying with H.264 high profile 4:2:2 in an mp4 file) I get the following pleasingly psychedelic/impressionistic result :

  

  There’s clearly something motion-vectory going on here !

  And if I let FFMPEG manage its own buffers with the H.264 input by not overriding AVCodecContext::get_buffer2, I can make a copy from the resulting frame to my desired destination buffer and get good results.

  Here’s my decoder method, _frame and _codecCtx are object members of type AVFrame* and AVCodecContext* respectively. They get alloc’d and init’d in the constructor.

          virtual const DecodeResult decode(const rv::sz_t toggle) override {
  
          _toggle = toggle & 1;
  
          using Flags_e = DecodeResultFlags_e;
  
          DecodeResult ans(Flags_e::kNoResult);
  
  
  
          AVPacket pkt;   // holds compressed data
  
          ::av_init_packet(&pkt);
  
          pkt.data = NULL;
  
          pkt.size = 0;
  
          int ret;
  
  
  
          // read the compressed frame to decode
  
          _err = av_read_frame(_fmtCtx, &pkt);
  
          if (_err < 0) {
  
              if (_err == AVERROR_EOF) {
  
                  ans.set(Flags_e::kEndOfFile);
  
                  _err = 0; // we can safely ignore EOF errors
  
                  return ans;
  
              } else {
  
                  baleOnFail(__PRETTY_FUNCTION__);
  
              }
  
          } 
  
  
  
          // send (compressed) packets to the decoder until it produces an uncompressed frame
  
          do {
  
  
  
              // sender
  
              _err = ::avcodec_send_packet(_codecCtx, &pkt);
  
              if (_err < 0) {
  
                  if (_err == AVERROR_EOF) {
  
                      _err = 0; // EOFs are ok
  
                      ans.set(Flags_e::kEndOfFile);
  
                      break;
  
                  } else {
  
                      baleOnFail(__PRETTY_FUNCTION__);
  
                  }
  
              }
  
  
  
              // receiver
  
              ret = ::avcodec_receive_frame (_codecCtx, _frame);
  
              if (ret == AVERROR(EAGAIN)) {
  
                  continue;
  
              } else if (ret == AVERROR_EOF) {
  
                  ans.set(Flags_e::kEndOfFile);
  
                  break;
  
              } else if (ret < 0) {
  
                  _err = ret;
  
                  baleOnFail(__PRETTY_FUNCTION__);
  
              } else {
  
                  ans.set(Flags_e::kGotFrame);
  
              }
  
  
  
              av_packet_unref (&pkt);
  
  
  
          } while (!ans.test(Flags_e::kGotFrame));        
  
  
  
          //packFrame(); <-- used to copy to client image
  
  
  
          return ans;
  
      }

  And here’s my override for get_buffer2

          int getVideoBuffer(struct AVCodecContext* ctx, AVFrame* frm) {
  
          // ensure frame pointers are all null
  
          if (frm->data[0] || frm->data[1] || frm->data[2] || frm->data[3]){
  
              ::strncpy (_errMsg, "non-null frame data pointer detected.", AV_ERROR_MAX_STRING_SIZE);
  
              return -1;
  
          }
  
  
  
          // get format descriptor, ensure it's valid.
  
          const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(static_cast<avpixelformat>(frm->format));
  
          if (!desc) {
  
              ::strncpy (_errMsg, "Pixel format descriptor not available.", AV_ERROR_MAX_STRING_SIZE);
  
              return AVERROR(EINVAL);
  
          }
  
  
  
          // for Video, extended data must point to the same place as data.
  
          frm->extended_data = frm->data;
  
  
  
          // set the data pointers to point at the Image data.
  
          int chan = 0;
  
          IMG* img = _imgs[_toggle];
  
          // initialize active channels
  
          for (; chan &lt; 3; ++chan) {
  
              frm->buf[chan] =  av_buffer_create (
  
                  static_cast(img->begin(chan)),
  
                  rv::unsigned_cast<int>(img->size(chan)),
  
                  Player::freeBufferCallback, // callback does nothing
  
                  reinterpret_cast(this),
  
                  0 // i.e. AV_BUFFER_FLAG_READONLY is not set
  
              );
  
              frm->linesize[chan] = rv::unsigned_cast<int>(img->stride(chan));
  
              frm->data[chan] = frm->buf[chan]->data;
  
          }
  
          // zero out inactive channels
  
          for (; chan &lt; AV_NUM_DATA_POINTERS; ++chan) {
  
              frm->data[chan] = NULL;
  
              frm->linesize[chan] = 0;
  
          }
  
          return 0;
  
      }
  
  </int></int></avpixelformat>

  I can reason that the codec needs to keep reference frames in memory and so I’m not really surprised that this isn’t working, but I’ve not been able to figure out how to have it deliver clean decoded frames to client memory. I thought that AVFrame::key_frame would have been a clue, but, after observing its behaviour in gdb, it doesn’t provide a useful trigger for when to allocate AVFrame::bufs from the buffer pool and when they can be initialized to point at client memory.

  Grateful for any help !

• Trouble with CoCCA Registry

  7 octobre 2012, par Multimedia Mike — General

  I’ve been rather despondent all week. People who see me daily could readily identify this fact. Unfortunately, the exact reason was difficult to adequately explain. The problems that nerds deal with…

  When A Domain Expires
  As a few people noticed, the multimedia.cx domain and all of it’s subdomains didn’t work this last week. The problem started on Monday, October 1. Whose fault ? Well, fundamentally, I neglected to renew the domain name in time. However, I prefer to place the blame on the .cx domain registrar, CoCCA Registry. You see, they have never developed the technology to email a domain holder with a notice that their domain is about to expire or has already expired.

  This domain is the only one I have ever held so I don’t have a lot of experience in this matter. I wondered if I was crazy for thinking it would be normal for a registrar to send an email or 2 with status updates about your domain. I get the impression from speaking with others that this is indeed normal. I have 3 different email addresses listed under my account at the registrar– 2 at multimedia.cx and a backup gmail account. I checked spam folders after this incident. Then I remembered that I have never received any email notifications from them (although password reset emails show up, so that part thankfully works). Also, their support emails are black holes.

  So, I guess the moral is : be wary of dealing with CoCCA Registry. However, they seem to be the only way to register domains under a wide variety of uncommon country codes.

  By Friday, the domain appeared to have been reinstated, even through the status was officially listed as “renewal-pending” according to the web-based management console. Eventually, as cached DNS results started to time out throughout the day, I started seeing subdomains come back. I excitedly used the ‘dig’ command to count down the seconds until gamemusic.multimedia.cx was accessible on the network I was on (the number after the domain name is the time-to-live or ‘TTL’ value) :

  $ dig +nocmd gamemusic.multimedia.cx +noall +answer
  gamemusic.multimedia.cx. 3      IN      A       174.143.152.251
  $ dig +nocmd gamemusic.multimedia.cx +noall +answer
  gamemusic.multimedia.cx. 2      IN      A       174.143.152.251
  $ dig +nocmd gamemusic.multimedia.cx +noall +answer
  gamemusic.multimedia.cx. 1      IN      A       174.143.152.251
  $ dig +nocmd gamemusic.multimedia.cx +noall +answer
  gamemusic.multimedia.cx. 12962  IN      A       207.45.186.114
  

  Finally, today (Saturday), I received a receipt confirming that the domain has been renewed.

  8 Years Old
  Incidentally, happy eighth birthday to multimedia.cx. It was September, 2004 when I decided to branch out from a simple ISP-based web presence.

  People often ask why I went with the .cx TLD. When I decided I wanted a proper domain name 8 years ago, I found that multimedia.X was already taken for just about every TLD value of X. .cx was a notable exception and was distinctive enough (speaking of .X, though, I see that multimedia.xxx is still up for grabs as of this writing ; I imagine that would come with a whole other set of problems).

  It’s funny that tech nerds often rail against outsourcing too much — email, storage, computing power, web hosting — all to some type of cloud provider under the premise that it could easily be taken away. But this episode teaches me that even having your own domain name is no guarantee of a solid online presence.

  Meanwhile, I have taken proactive steps to avert this same situation from arising again :

  
  
  

  Barring a lack of automated emails from the registrar, I hope a Google Calendar reminder set up a month ahead of expiration will do the trick.

• FFmpeg transcoding video H.264 -> AV1 leads to distorted image

  21 juin 2023, par user1584149

  I'm reading video from stdin via pipe similar to this one Python gets stuck at pipe.stdin.write(image.tostring())

  


  FFmpeg is using libsvtav1 codec with options according to documentation

  


  ffmpeg -y -f rawvideo -i pipe:0 -s {frame_width}x{frame_height} -r {frame_rate} -c:a copy -c:v libsvtav1 -preset 6 -crf 30 -svtav1-params "color-format=1:film-grain-denoise=0:mbr=2M" {output_file} 


  


  Here's couple of details about used FFmpeg version as well as input video

  


  ffmpeg version n5.1.3-14-ge5b5dd6653-20230621 Copyright (c) 2000-2022 the FFmpeg developers
  built with gcc 13.1.0 (crosstool-NG 1.25.0.196_227d99d)
  configuration: --prefix=/ffbuild/prefix --pkg-config-flags=--static --pkg-config=pkg-config --cross-prefix=x86_64-ffbuild-linux-gnu- --arch=x86_64 --target-os=linux --enable-gpl --enable-version3 --disable-debug --enable-iconv --enable-libxml2 --enable-zlib --enable-libfreetype --enable-libfribidi --enable-gmp --enable-openssl --enable-lzma --enable-fontconfig --enable-libvorbis --enable-opencl --enable-libpulse --enable-libvmaf --enable-libxcb --enable-xlib --enable-amf --enable-libaom --enable-libaribb24 --enable-avisynth --disable-chromaprint --enable-libdav1d --enable-libdavs2 --disable-libfdk-aac --enable-ffnvcodec --enable-cuda-llvm --enable-frei0r --enable-libgme --enable-libkvazaar --enable-libass --enable-libbluray --enable-libjxl --enable-libmp3lame --enable-libopus --enable-librist --enable-libssh --enable-libtheora --enable-libvpx --enable-libwebp --enable-lv2 --disable-openal --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenh264 --enable-libopenjpeg --enable-libopenmpt --enable-librav1e --enable-librubberband --disable-schannel --enable-sdl2 --enable-libsoxr --enable-libsrt --enable-libsvtav1 --enable-libtwolame --enable-libuavs3d --enable-libdrm --enable-vaapi --enable-libvidstab --enable-vulkan --enable-libshaderc --disable-libplacebo --enable-libx264 --enable-libx265 --enable-libxavs2 --enable-libxvid --enable-libzimg --enable-libzvbi --extra-cflags=-DLIBTWOLAME_STATIC --extra-cxxflags= --extra-ldflags=-pthread --extra-ldexeflags=-pie --extra-libs='-ldl -lgomp' --extra-version=20230621
  libavutil      57. 28.100 / 57. 28.100
  libavcodec     59. 37.100 / 59. 37.100
  libavformat    59. 27.100 / 59. 27.100
  libavdevice    59.  7.100 / 59.  7.100
  libavfilter     8. 44.100 /  8. 44.100
  libswscale      6.  7.100 /  6.  7.100
  libswresample   4.  7.100 /  4.  7.100
  libpostproc    56.  6.100 / 56.  6.100
Input #0, rawvideo, from 'pipe:0':
  Duration: N/A, start: 0.000000, bitrate: 331776 kb/s
  Stream #0:0: Video: rawvideo (I420 / 0x30323449), yuv420p, 1280x720, 331776 kb/s, 30 tbr, 30 tbn
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo (native) -> av1 (libsvtav1))
Svt[info]: -------------------------------------------
Svt[info]: SVT [version]:   SVT-AV1 Encoder Lib v1.5.0-12-g0f8b3a81
Svt[info]: SVT [build]  :   GCC 13.1.0   64 bit
Svt[info]: LIB Build date: Jun 20 2023 23:48:14
Svt[info]: -------------------------------------------


  


  The output video transcoded by SVT-AV1 codec is blemished as you can see on the images below. Normally I would say it could be caused by wrong pixel format, but input stream has yuv420 format what is the same as encoder's pixel format parameter —color-format.

  


  Please share your experience or ideas how to get it transcoding correctly.

  


  Thanks in advance.