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• How to port signal() to sigaction() ?

  28 septembre 2016, par Shark

  due to recent problems discovered with NDK12 and NDK13b2, i’m thinking of ’porting’ libx264’s use of signal() (and missing bsd_signal() in ndk12) to use sigaction() instead.

  The problem is, I’m not quite sure what’s the simple&fastest way to replace signal() calls with sigaction() ones.

  For all i see, it’s mainly used in x264-snapshot/common/cpu.c in the following manner :

  using the following signal handler :

  static void sigill_handler( int sig )
  
  {
  
      if( !canjump )
  
      {
  
          signal( sig, SIG_DFL );
  
          raise( sig );
  
      }
  
  
  
      canjump = 0;
  
      siglongjmp( jmpbuf, 1 );
  
  }

  This is the problematic x264_cpu_detect function... currently, i’m guessing i only need to tackle the ARM version, but i’ ; ; still have to replace all occurances of signal() with sigaction() so i might just cover both of them to get the thing building...

  FYI - the NDK13 beta2 still has "unstable" libc and the build doesn’t fail on this part, but rather the first invocation of the rand() function somewhere else... So i’m out of luck and replacing the signal() calls might be better than just waiting for the official NDK13 release. I’m doing this to get rid of text-relocations so i can run the library (and doubango) on API 24 (Android N)

  the problematic part of function that invokes signal() :

  #elif SYS_LINUX
  
  
  
  uint32_t x264_cpu_detect( void )
  
  {
  
      static void (*oldsig)( int );
  
  
  
      oldsig = signal( SIGILL, sigill_handler );
  
      if( sigsetjmp( jmpbuf, 1 ) )
  
      {
  
          signal( SIGILL, oldsig );
  
          return 0;
  
      }
  
  
  
      canjump = 1;
  
      asm volatile( "mtspr 256, %0\n\t"
  
                    "vand 0, 0, 0\n\t"
  
                    :
  
                    : "r"(-1) );
  
      canjump = 0;
  
  
  
      signal( SIGILL, oldsig );
  
  
  
      return X264_CPU_ALTIVEC;
  
  }
  
  #endif
  
  
  
  #elif ARCH_ARM
  
  
  
  void x264_cpu_neon_test( void );
  
  int x264_cpu_fast_neon_mrc_test( void );
  
  
  
  uint32_t x264_cpu_detect( void )
  
  {
  
      int flags = 0;
  
  #if HAVE_ARMV6
  
      flags |= X264_CPU_ARMV6;
  
  
  
      // don't do this hack if compiled with -mfpu=neon
  
  #if !HAVE_NEON
  
      static void (* oldsig)( int );
  
      oldsig = signal( SIGILL, sigill_handler );
  
      if( sigsetjmp( jmpbuf, 1 ) )
  
      {
  
          signal( SIGILL, oldsig );
  
          return flags;
  
      }
  
  
  
      canjump = 1;
  
      x264_cpu_neon_test();
  
      canjump = 0;
  
      signal( SIGILL, oldsig );
  
  #endif
  
  
  
      flags |= X264_CPU_NEON;
  
  
  
      // fast neon -> arm (Cortex-A9) detection relies on user access to the
  
      // cycle counter; this assumes ARMv7 performance counters.
  
      // NEON requires at least ARMv7, ARMv8 may require changes here, but
  
      // hopefully this hacky detection method will have been replaced by then.
  
      // Note that there is potential for a race condition if another program or
  
      // x264 instance disables or reinits the counters while x264 is using them,
  
      // which may result in incorrect detection and the counters stuck enabled.
  
      // right now Apple does not seem to support performance counters for this test
  
  #ifndef __MACH__
  
      flags |= x264_cpu_fast_neon_mrc_test() ? X264_CPU_FAST_NEON_MRC : 0;
  
  #endif
  
      // TODO: write dual issue test? currently it's A8 (dual issue) vs. A9 (fast      mrc)
  
  #endif
  
      return flags;
  
  }
  
  
  
  #else
  
  
  
  uint32_t x264_cpu_detect( void )
  
  {
  
      return 0;
  
  }

  So the question is really this : what would be the quickest/easiest//fastest way to replace the signal() calls with sigaction() ones while preserving the current functionality ?

  EDIT :
  The reason i’m trying to get rid of signal() are these build errors :

  /home/devshark/SCRATCH/doubango/thirdparties/android/armv5te/lib/dist/libx264.a(cpu.o):cpu.c:function sigill_handler: error: undefined reference to 'bsd_signal'
  
  
  
  /home/devshark/SCRATCH/doubango/thirdparties/android/armv5te/lib/dist/libx264.a(cpu.o):cpu.c:function x264_cpu_detect: error: undefined reference to 'bsd_signal'
  
  /home/devshark/SCRATCH/doubango/thirdparties/android/armv5te/lib/dist/libx264.a(cpu.o):cpu.c:function x264_cpu_detect: error: undefined reference to 'bsd_signal'
  
  
  
  /home/devshark/SCRATCH/doubango/thirdparties/android/armv5te/lib/dist/libx264.a(cpu.o):cpu.c:function x264_cpu_detect: error: undefined reference to 'bsd_signal'

  I already know that this is a known NDK12 problem, that might be solved by bringing bsd_signal back to the libc in NDK13. However, in it’ beta state with it’s unstable libc - it’s currently missing the rand() function and simply waiting for it might not do the trick. But in the worst-case scenario, i guess i’ll just have to wait for it and retry after it’s release.

  But as it currently is, the prebuilt version of the library i want to use has text-relocations and is being rejected by phones running newer API / version of the android OS.

  EDIT2 :
  I also know that signal() usually works by using sigaction() under the hood, but maybe i won’t get bsd_signal related build-errors... since i’m suspecting that this one isn’t using it. It’s obviously using bsd_signal, which may or may not be the same underlying thing :/

• How to port signal() to sigaction() ?

  28 septembre 2016, par Shark

  due to recent problems discovered with NDK12 and NDK13b2, i’m thinking of ’porting’ libx264’s use of signal() (and missing bsd_signal() in ndk12) to use sigaction() instead.

  The problem is, I’m not quite sure what’s the simple&fastest way to replace signal() calls with sigaction() ones.

  For all i see, it’s mainly used in x264-snapshot/common/cpu.c in the following manner :

  using the following signal handler :

  static void sigill_handler( int sig )
  
  {
  
      if( !canjump )
  
      {
  
          signal( sig, SIG_DFL );
  
          raise( sig );
  
      }
  
  
  
      canjump = 0;
  
      siglongjmp( jmpbuf, 1 );
  
  }

  This is the problematic x264_cpu_detect function... currently, i’m guessing i only need to tackle the ARM version, but i’ ; ; still have to replace all occurances of signal() with sigaction() so i might just cover both of them to get the thing building...

  FYI - the NDK13 beta2 still has "unstable" libc and the build doesn’t fail on this part, but rather the first invocation of the rand() function somewhere else... So i’m out of luck and replacing the signal() calls might be better than just waiting for the official NDK13 release. I’m doing this to get rid of text-relocations so i can run the library (and doubango) on API 24 (Android N)

  the problematic part of function that invokes signal() :

  #elif SYS_LINUX
  
  
  
  uint32_t x264_cpu_detect( void )
  
  {
  
      static void (*oldsig)( int );
  
  
  
      oldsig = signal( SIGILL, sigill_handler );
  
      if( sigsetjmp( jmpbuf, 1 ) )
  
      {
  
          signal( SIGILL, oldsig );
  
          return 0;
  
      }
  
  
  
      canjump = 1;
  
      asm volatile( "mtspr 256, %0\n\t"
  
                    "vand 0, 0, 0\n\t"
  
                    :
  
                    : "r"(-1) );
  
      canjump = 0;
  
  
  
      signal( SIGILL, oldsig );
  
  
  
      return X264_CPU_ALTIVEC;
  
  }
  
  #endif
  
  
  
  #elif ARCH_ARM
  
  
  
  void x264_cpu_neon_test( void );
  
  int x264_cpu_fast_neon_mrc_test( void );
  
  
  
  uint32_t x264_cpu_detect( void )
  
  {
  
      int flags = 0;
  
  #if HAVE_ARMV6
  
      flags |= X264_CPU_ARMV6;
  
  
  
      // don't do this hack if compiled with -mfpu=neon
  
  #if !HAVE_NEON
  
      static void (* oldsig)( int );
  
      oldsig = signal( SIGILL, sigill_handler );
  
      if( sigsetjmp( jmpbuf, 1 ) )
  
      {
  
          signal( SIGILL, oldsig );
  
          return flags;
  
      }
  
  
  
      canjump = 1;
  
      x264_cpu_neon_test();
  
      canjump = 0;
  
      signal( SIGILL, oldsig );
  
  #endif
  
  
  
      flags |= X264_CPU_NEON;
  
  
  
      // fast neon -> arm (Cortex-A9) detection relies on user access to the
  
      // cycle counter; this assumes ARMv7 performance counters.
  
      // NEON requires at least ARMv7, ARMv8 may require changes here, but
  
      // hopefully this hacky detection method will have been replaced by then.
  
      // Note that there is potential for a race condition if another program or
  
      // x264 instance disables or reinits the counters while x264 is using them,
  
      // which may result in incorrect detection and the counters stuck enabled.
  
      // right now Apple does not seem to support performance counters for this test
  
  #ifndef __MACH__
  
      flags |= x264_cpu_fast_neon_mrc_test() ? X264_CPU_FAST_NEON_MRC : 0;
  
  #endif
  
      // TODO: write dual issue test? currently it's A8 (dual issue) vs. A9 (fast      mrc)
  
  #endif
  
      return flags;
  
  }
  
  
  
  #else
  
  
  
  uint32_t x264_cpu_detect( void )
  
  {
  
      return 0;
  
  }

  So the question is really this : what would be the quickest/easiest//fastest way to replace the signal() calls with sigaction() ones while preserving the current functionality ?

  EDIT :
  The reason i’m trying to get rid of signal() are these build errors :

  /home/devshark/SCRATCH/doubango/thirdparties/android/armv5te/lib/dist/libx264.a(cpu.o):cpu.c:function sigill_handler: error: undefined reference to 'bsd_signal'
  
  
  
  /home/devshark/SCRATCH/doubango/thirdparties/android/armv5te/lib/dist/libx264.a(cpu.o):cpu.c:function x264_cpu_detect: error: undefined reference to 'bsd_signal'
  
  /home/devshark/SCRATCH/doubango/thirdparties/android/armv5te/lib/dist/libx264.a(cpu.o):cpu.c:function x264_cpu_detect: error: undefined reference to 'bsd_signal'
  
  
  
  /home/devshark/SCRATCH/doubango/thirdparties/android/armv5te/lib/dist/libx264.a(cpu.o):cpu.c:function x264_cpu_detect: error: undefined reference to 'bsd_signal'

  I already know that this is a known NDK12 problem, that might be solved by bringing bsd_signal back to the libc in NDK13. However, in it’ beta state with it’s unstable libc - it’s currently missing the rand() function and simply waiting for it might not do the trick. But in the worst-case scenario, i guess i’ll just have to wait for it and retry after it’s release.

  But as it currently is, the prebuilt version of the library i want to use has text-relocations and is being rejected by phones running newer API / version of the android OS.

  EDIT2 :
  I also know that signal() usually works by using sigaction() under the hood, but maybe i won’t get bsd_signal related build-errors... since i’m suspecting that this one isn’t using it. It’s obviously using bsd_signal, which may or may not be the same underlying thing :/

• FFmpeg filter config with aecho fails to configure all the links and formats - avfilter_graph_config

  23 janvier 2021, par cs guy

  I am following the official tutorial of FFMpeg to create a filter chain. This tutorial shows how to pass data through a chain as :

  


  


  The filter chain it uses is : * (input) -> abuffer -> volume ->
aformat -> abuffersink -> (output)

  


  


  Here is my code - sorry for boiler code, it is just ffmpeg way :(

  


      frame = av_frame_alloc();
    filterGraph = avfilter_graph_alloc();

    if (!frame) {
        *mediaLoadPointer = FAILED_TO_LOAD;
        LOGE("FXProcessor::FXProcessor Could not allocate memory for frame");
        return;
    }

    if (!filterGraph) {
        *mediaLoadPointer = FAILED_TO_LOAD;
        LOGE("FXProcessor::FXProcessor FXProcessor! %s", av_err2str(AVERROR(ENOMEM)));
        return;
    }

    const AVFilter *abuffer;
    const AVFilter *abuffersink;
    AVFilterContext *aformat_ctx;
    const AVFilter *aformat;
    AVFilterContext *choisen_beat_fx_ctx;
    const AVFilter *choisen_beat_fx;

    /* Create the abuffer filter;
     * it will be used for feeding the data into the graph. */
    abuffer = avfilter_get_by_name("abuffer");
    if (!abuffer) {
        *mediaLoadPointer = FAILED_TO_LOAD;
        LOGE("FXProcessor::FXProcessor Could not find the abuffer filter!");
        return;
    }
    abuffer_ctx = avfilter_graph_alloc_filter(filterGraph, abuffer, "src");
    if (!abuffer_ctx) {
        *mediaLoadPointer = FAILED_TO_LOAD;
        LOGE("FXProcessor::FXProcessor Could not allocate the abuffer_ctx instance! %s",
             av_err2str(AVERROR(ENOMEM)));
        return;
    }

    char ch_layout[64];
    /* Set the filter options through the AVOptions API. */
    av_get_channel_layout_string(ch_layout, sizeof(ch_layout), 0, AV_CH_LAYOUT_STEREO);
    av_opt_set(abuffer_ctx, "channel_layout", ch_layout, AV_OPT_SEARCH_CHILDREN);
    av_opt_set(abuffer_ctx, "sample_fmt", av_get_sample_fmt_name(AV_SAMPLE_FMT_FLT),
               AV_OPT_SEARCH_CHILDREN);
    av_opt_set_q(abuffer_ctx, "time_base", (AVRational) {1, defaultSampleRate},
                 AV_OPT_SEARCH_CHILDREN);
    av_opt_set_int(abuffer_ctx, "sample_rate", defaultSampleRate, AV_OPT_SEARCH_CHILDREN);
    /* Now initialize the filter; we pass NULL options, since we have already
     * set all the options above. */

    if (avfilter_init_str(abuffer_ctx, nullptr) < 0) {
        *mediaLoadPointer = FAILED_TO_LOAD;
        LOGE("FXProcessor::FXProcessor Could not initialize the abuffer filter!");
        return;
    }

    // TODO: select FX's dynamically
    /* Create aecho filter. */
    if (true) {

        choisen_beat_fx = avfilter_get_by_name("volume");
        if (!choisen_beat_fx) {
            *mediaLoadPointer = FAILED_TO_LOAD;
            LOGE("FXProcessor::FXProcessor Could not find the aecho filter!");
            return;
        }

        choisen_beat_fx_ctx = avfilter_graph_alloc_filter(filterGraph, choisen_beat_fx, "echo");
        if (!choisen_beat_fx_ctx) {
            *mediaLoadPointer = FAILED_TO_LOAD;
            LOGE("FXProcessor::FXProcessor Could not allocate the choisen_beat_fx_ctx instance! %s",
                 av_err2str(AVERROR(ENOMEM)));
            return;
        }

        av_opt_set    (choisen_beat_fx_ctx, "volume",     AV_STRINGIFY(0.5), AV_OPT_SEARCH_CHILDREN);

        if (avfilter_init_str(choisen_beat_fx_ctx, nullptr) < 0) {
            *mediaLoadPointer = FAILED_TO_LOAD;
            LOGE("FXProcessor::FXProcessor Could not initialize the choisen_beat_fx_ctx filter!");
            return;
        }
    }

    /* Create the aformat filter;
     * it ensures that the output is of the format we want. */
    aformat = avfilter_get_by_name("aformat");
    if (!aformat) {
        *mediaLoadPointer = FAILED_TO_LOAD;
        LOGE("FXProcessor::FXProcessor Could not find the aformat filter!");
        return;
    }
    aformat_ctx = avfilter_graph_alloc_filter(filterGraph, aformat, "aformat");
    if (!aformat_ctx) {
        *mediaLoadPointer = FAILED_TO_LOAD;
        LOGE("FXProcessor::FXProcessor Could not allocate the aformat instance!");
        return;
    }

    av_opt_set(aformat_ctx, "sample_fmts", av_get_sample_fmt_name(AV_SAMPLE_FMT_FLT),
               AV_OPT_SEARCH_CHILDREN);
    av_opt_set_int(aformat_ctx, "sample_rates", defaultSampleRate, AV_OPT_SEARCH_CHILDREN);
    av_get_channel_layout_string(ch_layout, sizeof(ch_layout), 0, AV_CH_LAYOUT_STEREO);
    av_opt_set(aformat_ctx, "channel_layouts", ch_layout, AV_OPT_SEARCH_CHILDREN);

    if (avfilter_init_str(aformat_ctx, nullptr) < 0) {
        *mediaLoadPointer = FAILED_TO_LOAD;
        LOGE("FXProcessor::FXProcessor Could not initialize the aformat filter!");
        return;
    }

    /* Finally create the abuffersink filter;
     * it will be used to get the filtered data out of the graph. */
    abuffersink = avfilter_get_by_name("abuffersink");
    if (!abuffersink) {
        *mediaLoadPointer = FAILED_TO_LOAD;
        LOGE("FXProcessor::FXProcessor Could not find the abuffersink filter!");
        return;
    }

    abuffersink_ctx = avfilter_graph_alloc_filter(filterGraph, abuffersink, "sink");
    if (!abuffersink_ctx) {
        *mediaLoadPointer = FAILED_TO_LOAD;
        LOGE("FXProcessor::FXProcessor Could not allocate the abuffersink instance!");
        return;
    }

    /* This filter takes no options. */
    if (avfilter_init_str(abuffersink_ctx, nullptr) < 0) {
        *mediaLoadPointer = FAILED_TO_LOAD;
        LOGE("FXProcessor::FXProcessor Could not initialize the abuffersink instance.!");
        return;
    }

    /* Connect the filters;
     * in this simple case the filters just form a linear chain. */
    if (avfilter_link(abuffer_ctx, 0, choisen_beat_fx_ctx, 0) != 0) {
        *mediaLoadPointer = FAILED_TO_LOAD;
        LOGE("FXProcessor::FXProcessor Error connecting filters.!");
        return;
    }
    if (avfilter_link(choisen_beat_fx_ctx, 0, aformat_ctx, 0) != 0) {
        *mediaLoadPointer = FAILED_TO_LOAD;
        LOGE("FXProcessor::FXProcessor Error connecting filters.!");
        return;
    }
    if (avfilter_link(aformat_ctx, 0, abuffersink_ctx, 0) != 0) {
        *mediaLoadPointer = FAILED_TO_LOAD;
        LOGE("FXProcessor::FXProcessor Error connecting filters.!");
        return;
    }

    /* Configure the graph. */
    if (avfilter_graph_config(filterGraph, nullptr) < 0) {
        *mediaLoadPointer = FAILED_TO_LOAD;
        LOGE("FXProcessor::FXProcessor Error configuring the filter graph!");
        return;
    }


  


  This code works fine when the chain is

  


  


  

  • (input) -> abuffer -> aecho-> aformat -> abuffersink -> (output)

  


  


  


  However, I would like to use adelay instead of volume filter. So I want :

  


  


  The filter chain it uses is : * (input) -> abuffer -> volume ->
aformat -> abuffersink -> (output)

  


  


  I changed the code at

  


  choisen_beat_fx = avfilter_get_by_name("volume");


  


  to

  


  choisen_beat_fx = avfilter_get_by_name("aecho");


  


  and removed the line

  


  av_opt_set    (choisen_beat_fx_ctx, "volume",     AV_STRINGIFY(0.5), AV_OPT_SEARCH_CHILDREN);


  


  everything goes smooth until the last line.
avfilter_graph_config fails and returns negative value. Functions document :

  


  


  avfilter_graph_config : Check validity and configure all the links and
formats in the graph.

  


  


  So my guess is I need extra links to insert aecho to my chain ? How can I insert aecho into my filter chain ?