[FFmpeg-devel] [PATCH 2/4] lavd: add device capabilities API

Nicolas George george at nsup.org
Sun Feb 16 12:45:20 CET 2014


Le tridi 23 pluviôse, an CCXXII, Lukasz M a écrit :
> It is shared in different structs.

And unshared in, at least, AVCodecContext. But that does not matter much.

> >
> > > +
> > > +    /**
> > > +     * Initialize device capabilities submodule.
> > > +     * @see avdevice_capabilities_create() for more details.
> > > +     */
> > > +    int (*create_device_capabilities)(struct AVFormatContext *s, void
> > *caps);
> > > +
> > > +    /**
> > > +     * Apply currently set device capabilities to device context.
> > > +     * @see avdevice_capabilities_apply() for more details.
> > > +     */
> > > +    int (*apply_device_capabilities)(struct AVFormatContext *s, void
> > *caps,
> > > +                                     int strategy);
> > > +
> > > +    /**
> > > +     * Free device capabilities submodule.
> > > +     * @see avdevice_capabilities_free() for more details.
> > > +     */
> > > +    int (*free_device_capabilities)(struct AVFormatContext *s, void
> > *caps);
> >
> > Would it make sense to share these between in and out formats?
> >
> 
> Hmmm, I don't understand how?

Instead of having the three fields create_device_capabilities,
apply_device_capabilities and free_device_capabilities in both AVInputFormat
and AVOutputFormat, you could just declare a single structure
AVDeviceQueryMethods with these three fields, and add a pointer to it in
both AVInputFormat and AVOutputFormat.

That was just a random thought.

> 
> 
> Updated patch attached

> From 5db27e54528f64ebf36519311d4c95648228f1b3 Mon Sep 17 00:00:00 2001
> From: Lukasz Marek <lukasz.m.luki at gmail.com>
> Date: Fri, 7 Feb 2014 14:35:01 +0100
> Subject: [PATCH 2/4] lavd: add device capabilities API
> 
> TODO: bump minors, update APIchages
> 
> Signed-off-by: Lukasz Marek <lukasz.m.luki at gmail.com>
> ---
>  libavdevice/avdevice.c |  100 ++++++++++++++++++++++++++++++++++++++++++++++++
>  libavdevice/avdevice.h |   79 ++++++++++++++++++++++++++++++++++++++
>  libavformat/avformat.h |   36 +++++++++++++++++
>  3 files changed, 215 insertions(+)
> 
> diff --git a/libavdevice/avdevice.c b/libavdevice/avdevice.c
> index 92cb834..c3f8ea4 100644
> --- a/libavdevice/avdevice.c
> +++ b/libavdevice/avdevice.c
> @@ -17,9 +17,50 @@
>   */
>  
>  #include "libavutil/avassert.h"
> +#include "libavcodec/avcodec.h"
>  #include "avdevice.h"
>  #include "config.h"
>  
> +#define E AV_OPT_FLAG_ENCODING_PARAM
> +#define D AV_OPT_FLAG_DECODING_PARAM
> +#define A AV_OPT_FLAG_AUDIO_PARAM
> +#define V AV_OPT_FLAG_VIDEO_PARAM
> +#define OFFSET(x) offsetof(AVDeviceCapabilitiesQuery, x)
> +
> +const AVOption av_device_capabilities[] = {
> +    { "device_name", "device name", OFFSET(device_name), AV_OPT_TYPE_STRING,
> +        {.str = NULL}, 0, 0, E|D|A|V },
> +    { "codec", "codec", OFFSET(codec), AV_OPT_TYPE_INT,
> +        {.i64 = -1}, -1, INT_MAX, E|D|A|V },
> +    { "format", "format", OFFSET(format), AV_OPT_TYPE_INT,
> +        {.i64 = -1}, -1, INT_MAX, E|D|A|V },
> +
> +    { "sample_rate", "sample rate", OFFSET(sample_rate), AV_OPT_TYPE_INT,
> +        {.i64 = -1}, -1, INT_MAX, E|D|A },
> +    { "channels", "channels", OFFSET(channels), AV_OPT_TYPE_INT,
> +        {.i64 = -1}, -1, INT_MAX, E|D|A },
> +    { "channel_layout", "channel layout", OFFSET(channel_layout), AV_OPT_TYPE_INT64,
> +        {.i64 = -1}, -1, INT_MAX, E|D|A },
> +
> +    { "window_width", "window width", OFFSET(window_width), AV_OPT_TYPE_INT,
> +        {.i64 = -1}, -1, INT_MAX, E|D|V },
> +    { "window_height", "window height", OFFSET(window_height), AV_OPT_TYPE_INT,
> +        {.i64 = -1}, -1, INT_MAX, E|D|V },

> +    { "frame_width", "frame width", OFFSET(frame_width), AV_OPT_TYPE_INT,
> +        {.i64 = -1}, -1, INT_MAX, E|D|V },
> +    { "frame_height", "frame height", OFFSET(frame_height), AV_OPT_TYPE_INT,
> +        {.i64 = -1}, -1, INT_MAX, E|D|V },

This version still has one open issue: how does it express a limited set of
frame sizes. For example, if a webcam supports exactly 640×480 and 320×240.
Does it return { 320, 640 } for the width and { 240, 480 } for the height?
Is the application supposed to try each width in turn and query the
corresponding range for height? It works, although it is a bit cumbersome,
but it is not intuitive: maybe add a comment, or do it like that in the
examples.

> +    { "fps", "fps", OFFSET(fps), AV_OPT_TYPE_RATIONAL,
> +        {.dbl = -1}, -1, INT_MAX, E|D|V },
> +    { NULL }
> +};
> +
> +#undef E
> +#undef D
> +#undef A
> +#undef V
> +#undef OFFSET
> +
>  unsigned avdevice_version(void)
>  {
>      av_assert0(LIBAVDEVICE_VERSION_MICRO >= 100);
> @@ -53,6 +94,65 @@ int avdevice_dev_to_app_control_message(struct AVFormatContext *s, enum AVDevToA
>      return s->control_message_cb(s, type, data, data_size);
>  }
>  
> +int avdevice_capabilities_create(AVDeviceCapabilitiesQuery **caps, AVFormatContext *s,
> +                                 AVDictionary **device_options)
> +{
> +    int ret;
> +    av_assert1(s && caps);
> +    av_assert1(s->iformat || s->oformat);
> +    if ((s->oformat && !s->oformat->create_device_capabilities) ||
> +        (s->iformat && !s->iformat->create_device_capabilities))
> +        return AVERROR(ENOSYS);
> +    *caps = av_mallocz(sizeof(**caps));
> +    if (!(*caps))
> +        return AVERROR(ENOMEM);
> +    (*caps)->device_context = s;
> +    if ((ret = av_opt_set_dict(s->priv_data, device_options)) < 0)
> +        goto fail;
> +    if (s->iformat) {
> +        if ((ret = s->iformat->create_device_capabilities(s, *caps)) < 0)
> +            goto fail;
> +    } else {
> +        if ((ret = s->oformat->create_device_capabilities(s, *caps)) < 0)
> +            goto fail;
> +    }
> +    av_opt_set_defaults(*caps);
> +    return 0;
> +  fail:
> +    av_freep(caps);
> +    return ret;
> +}
> +
> +int avdevice_capabilities_apply(AVDeviceCapabilitiesQuery *caps, AVFormatContext *s,
> +                               enum AVDeviceCapabilitiesApplyStrategy strategy)
> +{
> +    av_assert1(s);
> +    av_assert1(s->iformat || s->oformat);
> +    if (s->iformat) {
> +        if (!s->iformat->apply_device_capabilities)
> +            return AVERROR(ENOSYS);
> +        return s->iformat->apply_device_capabilities(s, caps, strategy);
> +    }
> +    if (!s->oformat->apply_device_capabilities)
> +        return AVERROR(ENOSYS);
> +    return s->oformat->apply_device_capabilities(s, caps, strategy);
> +}
> +
> +void avdevice_capabilities_free(AVDeviceCapabilitiesQuery **caps, AVFormatContext *s)
> +{
> +    av_assert1(s && caps);
> +    av_assert1(s->iformat || s->oformat);
> +    if (s->iformat) {
> +        if (s->iformat->free_device_capabilities)
> +            s->iformat->free_device_capabilities(s, *caps);
> +    } else {
> +        if (s->oformat->free_device_capabilities)
> +            s->oformat->free_device_capabilities(s, *caps);
> +    }
> +    av_free((*caps)->device_name);
> +    av_freep(caps);
> +}
> +
>  int avdevice_list_devices(AVFormatContext *s, AVDeviceInfoList **device_list)
>  {
>      av_assert1(s);
> diff --git a/libavdevice/avdevice.h b/libavdevice/avdevice.h
> index 7c98c3f..eb6a20f 100644
> --- a/libavdevice/avdevice.h
> +++ b/libavdevice/avdevice.h
> @@ -43,6 +43,9 @@
>   * @}
>   */
>  
> +#include "libavutil/log.h"
> +#include "libavutil/opt.h"
> +#include "libavutil/dict.h"
>  #include "libavformat/avformat.h"
>  
>  /**
> @@ -187,6 +190,82 @@ int avdevice_dev_to_app_control_message(struct AVFormatContext *s,
>                                          void *data, size_t data_size);
>  
>  /**
> + * Structure describes device settings.
> + *
> + * It is used by devices in conjuntion with av_device_capabilities AVOption table
> + * to to implement capabilities probing API based on AVOption API.
> + */
> +typedef struct AVDeviceCapabilitiesQuery {
> +    const AVClass *class;
> +    char *device_name;
> +    AVFormatContext *device_context;
> +    enum AVCodecID codec;
> +    int format;                          /**< AVSampleFormat or AVPixelFormat */
> +    int sample_rate;
> +    int channels;
> +    int64_t channel_layout;
> +    int window_width;
> +    int window_height;
> +    int frame_width;
> +    int frame_height;
> +    AVRational fps;
> +} AVDeviceCapabilitiesQuery;
> +
> +extern const AVOption av_device_capabilities[];
> +
> +enum AVDeviceCapabilitiesApplyStrategy {
> +    AVDEVICE_STRATEGY_APPLY_IF_VALID,                /**< apply settings when valid */
> +    AVDEVICE_STRATEGY_FIX_TO_THE_NEAREST,            /**< adjust structure only to the nearest valid value */
> +    AVDEVICE_STRATEGY_FIX_TO_THE_BEST,               /**< adjust structure only to the best valid value */
> +    AVDEVICE_STRATEGY_FIX_TO_THE_NEAREST_AND_APPLY,  /**< adjust values to the nearest valid value and apply */
> +    AVDEVICE_STRATEGY_FIX_TO_THE_BEST_AND_APPLY      /**< adjust values to the best valid value and apply */
> +};
> +
> +/**
> + * Initialize capabilities probing API based on AVOption API.
> + *
> + * avdevice_capabilities_free() must be called when query capabilities API is
> + * not used anymore.
> + *
> + * @note: It is not allowed to free device context before calling avdevice_capabilities_free().
> + *
> + * @param caps           device configuration
> + * @param s              device context
> + * @param device_options device options
> + * @return >= 0 on success, negative otherwise.
> + */
> +int avdevice_capabilities_create(AVDeviceCapabilitiesQuery **caps, AVFormatContext *s,
> +                                 AVDictionary **device_options);
> +
> +/**
> + * Apply set parameters to device context and release data allocated
> + * by avdevice_init_device_capabilities().
> + *
> + * All set capabilities are validated and tested. When configuration is not
> + * valid then adjustment takes place according to provided strategy.
> + * When it is required by provided strategy, set capabilities are applied into
> + * device context. Mapping between capablities and device settings are device-specific.
> + * In particular output device may not apply all parameters to the context,
> + * but use stream properties when avformat_write_header() is called.
> + *
> + * @param caps     device configuration
> + * @param s        device context
> + * @param strategy apply strategy
> + * @return 0 when configuration is not applied, 1 when configuration is applied,
> + *         negative on error.
> + */
> +int avdevice_capabilities_apply(AVDeviceCapabilitiesQuery *caps, AVFormatContext *s,
> +                                enum AVDeviceCapabilitiesApplyStrategy strategy);
> +
> +/**
> + * Free resources created by avdevice_capabilities_create()
> + *
> + * @param caps device configuration
> + * @param s    device context
> + */
> +void avdevice_capabilities_free(AVDeviceCapabilitiesQuery **caps, AVFormatContext *s);
> +
> +/**
>   * Structure describes basic parameters of the device.
>   */
>  typedef struct AVDeviceInfo {
> diff --git a/libavformat/avformat.h b/libavformat/avformat.h
> index 6595fea..854f0b3 100644
> --- a/libavformat/avformat.h
> +++ b/libavformat/avformat.h
> @@ -262,6 +262,7 @@
>  struct AVFormatContext;
>  
>  struct AVDeviceInfoList;
> +struct AVDeviceCapabilitiesQuery;
>  
>  /**
>   * @defgroup metadata_api Public Metadata API
> @@ -518,6 +519,22 @@ typedef struct AVOutputFormat {
>       * @see avdevice_list_devices() for more details.
>       */
>      int (*get_device_list)(struct AVFormatContext *s, struct AVDeviceInfoList *device_list);
> +    /**
> +     * Initialize device capabilities submodule.
> +     * @see avdevice_capabilities_create() for more details.
> +     */
> +    int (*create_device_capabilities)(struct AVFormatContext *s, struct AVDeviceCapabilitiesQuery *caps);
> +    /**
> +     * Apply currently set device capabilities to device context.
> +     * @see avdevice_capabilities_apply() for more details.
> +     */
> +    int (*apply_device_capabilities)(struct AVFormatContext *s,
> +                                     struct AVDeviceCapabilitiesQuery *caps, int strategy);
> +    /**
> +     * Free device capabilities submodule.
> +     * @see avdevice_capabilities_free() for more details.
> +     */
> +    int (*free_device_capabilities)(struct AVFormatContext *s, struct AVDeviceCapabilitiesQuery *caps);
>  } AVOutputFormat;
>  /**
>   * @}
> @@ -652,6 +669,25 @@ typedef struct AVInputFormat {
>       * @see avdevice_list_devices() for more details.
>       */
>      int (*get_device_list)(struct AVFormatContext *s, struct AVDeviceInfoList *device_list);
> +
> +    /**
> +     * Initialize device capabilities submodule.
> +     * @see avdevice_capabilities_create() for more details.
> +     */
> +    int (*create_device_capabilities)(struct AVFormatContext *s, struct AVDeviceCapabilitiesQuery *caps);
> +
> +    /**
> +     * Apply currently set device capabilities to device context.
> +     * @see avdevice_capabilities_apply() for more details.
> +     */
> +    int (*apply_device_capabilities)(struct AVFormatContext *s,
> +                                     struct AVDeviceCapabilitiesQuery *caps, int strategy);
> +
> +    /**
> +     * Free device capabilities submodule.
> +     * @see avdevice_capabilities_free() for more details.
> +     */
> +    int (*free_device_capabilities)(struct AVFormatContext *s, struct AVDeviceCapabilitiesQuery *caps);
>  } AVInputFormat;
>  /**
>   * @}

Regards,

-- 
  Nicolas George
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