Recherche avancée

Sur d’autres sites (4597)

• How to understand the given ffplay C code snippet ?

  20 juillet 2015, par Jerikc XIONG

  The following code snippet is from ffplay :

  static int decoder_decode_frame(Decoder *d, AVFrame *frame, AVSubtitle *sub) {
  
      int got_frame = 0;
  
  
  
      do {
  
          int ret = -1;
  
  
  
          if (d->queue->abort_request)
  
              return -1;
  
  
  
          if (!d->packet_pending || d->queue->serial != d->pkt_serial) {
  
              AVPacket pkt;
  
              do {
  
                  if (d->queue->nb_packets == 0)
  
                      SDL_CondSignal(d->empty_queue_cond);
  
                  if (packet_queue_get(d->queue, &pkt, 1, &d->pkt_serial) < 0)
  
                      return -1;
  
                  if (pkt.data == flush_pkt.data) {
  
                      avcodec_flush_buffers(d->avctx);
  
                      d->finished = 0;
  
                      d->next_pts = d->start_pts;
  
                      d->next_pts_tb = d->start_pts_tb;
  
                  }
  
              } while (pkt.data == flush_pkt.data || d->queue->serial != d->pkt_serial);
  
              av_free_packet(&d->pkt);
  
              d->pkt_temp = d->pkt = pkt;
  
              d->packet_pending = 1;
  
          }
  
  
  
          switch (d->avctx->codec_type) {
  
              case AVMEDIA_TYPE_VIDEO:
  
                  ret = avcodec_decode_video2(d->avctx, frame, &got_frame, &d->pkt_temp);
  
                  if (got_frame) {
  
                      if (decoder_reorder_pts == -1) {
  
                          frame->pts = av_frame_get_best_effort_timestamp(frame);
  
                      } else if (decoder_reorder_pts) {
  
                          frame->pts = frame->pkt_pts;
  
                      } else {
  
                          frame->pts = frame->pkt_dts;
  
                      }
  
                  }
  
                  break;
  
              case AVMEDIA_TYPE_AUDIO:
  
                  ret = avcodec_decode_audio4(d->avctx, frame, &got_frame, &d->pkt_temp);
  
                  if (got_frame) {
  
                      AVRational tb = (AVRational){1, frame->sample_rate};
  
                      if (frame->pts != AV_NOPTS_VALUE)
  
                          frame->pts = av_rescale_q(frame->pts, d->avctx->time_base, tb);
  
                      else if (frame->pkt_pts != AV_NOPTS_VALUE)
  
                          frame->pts = av_rescale_q(frame->pkt_pts, av_codec_get_pkt_timebase(d->avctx), tb);
  
                      else if (d->next_pts != AV_NOPTS_VALUE)
  
                          frame->pts = av_rescale_q(d->next_pts, d->next_pts_tb, tb);
  
                      if (frame->pts != AV_NOPTS_VALUE) {
  
                          d->next_pts = frame->pts + frame->nb_samples;
  
                          d->next_pts_tb = tb;
  
                      }
  
                  }
  
                  break;
  
              case AVMEDIA_TYPE_SUBTITLE:
  
                  ret = avcodec_decode_subtitle2(d->avctx, sub, &got_frame, &d->pkt_temp);
  
                  break;
  
          }
  
  
  
          if (ret < 0) {
  
              d->packet_pending = 0;
  
          } else {
  
              d->pkt_temp.dts =
  
              d->pkt_temp.pts = AV_NOPTS_VALUE;
  
              if (d->pkt_temp.data) {
  
                  if (d->avctx->codec_type != AVMEDIA_TYPE_AUDIO)
  
                      ret = d->pkt_temp.size;
  
                  d->pkt_temp.data += ret;
  
                  d->pkt_temp.size -= ret;
  
                  if (d->pkt_temp.size <= 0)
  
                      d->packet_pending = 0;
  
              } else {
  
                  if (!got_frame) {
  
                      d->packet_pending = 0;
  
                      d->finished = d->pkt_serial; // FLAG
  
                  }
  
              }
  
          }
  
      } while (!got_frame && !d->finished);
  
  
  
      return got_frame;
  
  }

  It’s difficult for me to understand the following code :

  d->finished = d->pkt_serial; // FLAG

  Can anyone help me ?

  Thanks.

• Android : Native Code, libx264

  11 septembre 2011, par NadavRub

  I am working with Android OS, my aim is doing propriotary imgproc and send the result as H264 video stream out of the device, for this, I will need to use a compression tool, I have considered the open source libx264 ( which got compiled on the Android env quite easily ).

  Having that said, does libx264 will know to identify the underling CPU/instruction set, OR, would I need to maintain a specialized binary for each CPU type ( eg. Nvidia/ARM ) ?

  The last thing I want is to maintain a specific version of code/binary for each CPU type...

  Any help would be appreciated.

   Nadav

• How to configure FFMPEG to generate position independent code on IOS

  8 juillet 2013, par madadi

  I am developing an app on iOS which makes use of FFMPEG for video decoding. I want to get 'position independent code' of FFMPEG working on my app. --enable-pic option in the FFMPEG configuration generates position independent code only if I set --disable-asm. I concluded this when I ran the otool on my app(otool -hv 'appname'). Below are the details :

  If I set --enable-pic alone, below is the output with otool :

  magic     cputype  cpusubtype  caps  filetype  ncmds  sizeofcmds  flags
  
  MH_MAGIC  ARM      V7          0x00  EXECUTE   29     3724        NOUNDEFS DYLDLINK TWOLEVEL WEAK_DEFINES BINDS_TO_WEAK

  If I set --enable-pic and --disable-asm below is the output with otool,

  magic     cputype  cpusubtype  caps  filetype  ncmds  sizeofcmds  flags
  
  MH_MAGIC  ARM      V7          0x00  EXECUTE   51     5520        NOUNDEFS DYLDLINK TWOLEVEL WEAK_DEFINES BINDS_TO_WEAK **PIE** 

  Below are my configuration settings for FFMPEG(build-ffmpeg-ios.sh) :

  if [  `uname` =  "Darwin" ]; then
  
    SEDCMD="sed -i '' "
  
  else
  
    SEDCMD="sed -i "
  
  fi
  
  
  
  
  
  make clean
  
  ./configure \
  
      --prefix=$PREFIX \
  
      --enable-version3 \
  
      --enable-static \
  
      --disable-shared \
  
      --disable-doc \
  
      --disable-ffmpeg \
  
      --disable-ffplay \
  
      --disable-ffprobe \
  
      --disable-ffserver \
  
      --disable-avdevice \
  
      --disable-avfilter \
  
      --disable-postproc \
  
      --enable-small \
  
      --cross-prefix="$DEVROOT/usr/bin/" \
  
      --enable-cross-compile \
  
      --target-os=darwin \
  
      --arch=$ARCH \
  
      --cpu=$CPU \
  
      --cc="$CC" \
  
      --as="$AS" \
  
      --extra-cflags="$CFLAGS" \
  
      --extra-ldflags="$CFLAGS" \
  
      --disable-symver \
  
      --disable-debug \
  
      --disable-indevs \
  
      --disable-encoders \
  
      --disable-bsfs \
  
      --enable-pic \
  
      --disable-filters \
  
      $CONFIGURE_FLAGS || exit 1;
  
  $SEDCMD 's/HAVE_INLINE_ASM 1/HAVE_INLINE_ASM 0/g' config.h
  
  make install || exit 1;

  And below is the make file I use(iOS.mk) :

  FFMPEG_LIBS := libavcodec.a libavformat.a libavutil.a libswscale.a
  
  
  
  IOS_ARMV7_FFMPEG_LIB := $(addprefix build/ios/armv7/lib/, $(FFMPEG_LIBS))
  
  
  
  IOS_UNI_FFMPEG_LIB := $(addprefix build/ios/universal/lib/, $(FFMPEG_LIBS))
  
  
  
  
  
  
  
  IPHONE_SDK_VERSION := "5.0"
  
  IPHONE_DEPLOY_SDK := "3.2"
  
  
  
  ALL_IOS_LIBS := $(IOS_UNI_FFMPEG_LIB) 
  
  
  
  build/ios/universal/lib/%.a : build/ios/armv7/lib/%.a
  
      mkdir -p build/ios/universal/lib
  
      lipo -create -output $@ $^
  
  
  
  
  
  
  
  $(IOS_ARMV7_FFMPEG_LIB): 
  
      export PREFIX="`$(ABSPATH) build/ios/armv7`" && \
  
      export ARCH="arm" && \
  
      export CPU="cortex-a8" && \
  
      export IOS_BASE_SDK="$(IPHONE_SDK_VERSION)" && \
  
      export IOS_DEPLOY_TGT="$(IPHONE_DEPLOY_SDK)" && \
  
      export CONFIGURE_FLAGS="--enable-neon" && \
  
      export PATH="`$(ABSPATH) venders`:$$PATH" && \
  
      cd venders/ffmpeg && bash ../iphone-compile.sh arm7 ../build-ffmpeg-ios.sh

  Can someone please help me with getting the FFMPEG up and running with both 'pic' and assembly optimization enabled. Without assembly optimizastion, FFMPEG would not be helpful to me as the video decoding is extremely slow.