Re: [PATCH v5 16/20] spice-gtk: Refactor the video decoding to use a more object oriented design.

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Hey,

On Thu, Aug 27, 2015 at 09:03:01PM +0200, Francois Gouget wrote:
> The video decoder no longer stores its internal state in the display_stream struct, or depend on it to know which frame to decode or store the decoded frame.
> This way adding alternative implementations will not pile all their implementation details in display_stream and have more flexibility for their implementation.

Please (applies to all your patches), limit your short log summary to
about 50 chars, and wrap the commit lines, see
http://chris.beams.io/posts/git-commit/#seven-rules

> 
> Signed-off-by: Francois Gouget <fgouget@xxxxxxxxxxxxxxx>
> ---
> 
> Changes since take 2:
>  - None.
> 
> 
>  src/channel-display-mjpeg.c | 140 +++++++++++++++++++++++++++++---------------
>  src/channel-display-priv.h  |  56 +++++++++++++-----
>  src/channel-display.c       |  65 +++++++++-----------
>  3 files changed, 165 insertions(+), 96 deletions(-)
> 
> diff --git a/src/channel-display-mjpeg.c b/src/channel-display-mjpeg.c
> index 95d5b33..37b28f7 100644
> --- a/src/channel-display-mjpeg.c
> +++ b/src/channel-display-mjpeg.c
> @@ -21,14 +21,38 @@
>  #include "spice-common.h"
>  #include "spice-channel-priv.h"
>  
> +typedef struct MJpegDecoder MJpegDecoder;
> +#define VIDEO_DECODER_T MJpegDecoder

I'd prefer that this #define VIDEO_DECODER_T templating magic is avoided

>  #include "channel-display-priv.h"
>  
> +
> +/* MJpeg decoder implementation */
> +
> +struct MJpegDecoder {
> +    VideoDecoder base;
> +
> +    /* ---------- The builtin mjpeg decoder ---------- */
> +
> +    SpiceMsgIn *frame_msg;
> +    struct jpeg_source_mgr         mjpeg_src;
> +    struct jpeg_decompress_struct  mjpeg_cinfo;
> +    struct jpeg_error_mgr          mjpeg_jerr;
> +
> +    /* ---------- Output frame data ---------- */
> +
> +    uint8_t *out_frame;
> +    uint32_t out_size;
> +};
> +
> +
> +/* ---------- The JPEG library callbacks ---------- */
> +
>  static void mjpeg_src_init(struct jpeg_decompress_struct *cinfo)
>  {
> -    display_stream *st = SPICE_CONTAINEROF(cinfo->src, display_stream, mjpeg_src);
> -    uint8_t *data;
> +    MJpegDecoder *decoder = SPICE_CONTAINEROF(cinfo->src, MJpegDecoder, mjpeg_src);
>  
> -    cinfo->src->bytes_in_buffer = stream_get_current_frame(st, &data);
> +    uint8_t *data;
> +    cinfo->src->bytes_in_buffer = spice_msg_in_frame_data(decoder->frame_msg, &data);
>      cinfo->src->next_input_byte = data;
>  }
>  
> @@ -49,68 +73,62 @@ static void mjpeg_src_term(struct jpeg_decompress_struct *cinfo)
>      /* nothing */
>  }
>  
> -G_GNUC_INTERNAL
> -void stream_mjpeg_init(display_stream *st)
> -{
> -    st->mjpeg_cinfo.err = jpeg_std_error(&st->mjpeg_jerr);
> -    jpeg_create_decompress(&st->mjpeg_cinfo);
> -
> -    st->mjpeg_src.init_source         = mjpeg_src_init;
> -    st->mjpeg_src.fill_input_buffer   = mjpeg_src_fill;
> -    st->mjpeg_src.skip_input_data     = mjpeg_src_skip;
> -    st->mjpeg_src.resync_to_restart   = jpeg_resync_to_restart;
> -    st->mjpeg_src.term_source         = mjpeg_src_term;
> -    st->mjpeg_cinfo.src               = &st->mjpeg_src;
> -}
>  
> -G_GNUC_INTERNAL
> -void stream_mjpeg_data(display_stream *st)
> +/* ---------- VideoDecoder's public API ---------- */
> +
> +static uint8_t* mjpeg_decoder_decode_frame(MJpegDecoder *decoder,
> +                                           SpiceMsgIn *frame_msg)
>  {
> -    gboolean back_compat = st->channel->priv->peer_hdr.major_version == 1;
> +    gboolean back_compat = decoder->base.stream->channel->priv->peer_hdr.major_version == 1;
>      int width;
>      int height;
>      uint8_t *dest;
>      uint8_t *lines[4];
>  
> -    stream_get_dimensions(st, &width, &height);
> -    dest = g_malloc0(width * height * 4);
> -
> -    g_free(st->out_frame);
> -    st->out_frame = dest;
> +    decoder->frame_msg = frame_msg;
> +    stream_get_dimensions(decoder->base.stream, frame_msg, &width, &height);
> +    if (decoder->out_size < width * height * 4) {
> +        if (decoder->out_frame) {
> +            free(decoder->out_frame);
> +        }

No need for the if()

> +        decoder->out_size = width * height * 4;
> +        decoder->out_frame = spice_malloc(decoder->out_size);
> +    }
> +    dest = decoder->out_frame;
>  
> -    jpeg_read_header(&st->mjpeg_cinfo, 1);
> +    jpeg_read_header(&decoder->mjpeg_cinfo, 1);
>  #ifdef JCS_EXTENSIONS
>      // requires jpeg-turbo
>      if (back_compat)
> -        st->mjpeg_cinfo.out_color_space = JCS_EXT_RGBX;
> +        decoder->mjpeg_cinfo.out_color_space = JCS_EXT_RGBX;
>      else
> -        st->mjpeg_cinfo.out_color_space = JCS_EXT_BGRX;
> +        decoder->mjpeg_cinfo.out_color_space = JCS_EXT_BGRX;
>  #else
>  #warning "You should consider building with libjpeg-turbo"
> -    st->mjpeg_cinfo.out_color_space = JCS_RGB;
> +    decoder->mjpeg_cinfo.out_color_space = JCS_RGB;
>  #endif
>  
>  #ifndef SPICE_QUALITY
> -    st->mjpeg_cinfo.dct_method = JDCT_IFAST;
> -    st->mjpeg_cinfo.do_fancy_upsampling = FALSE;
> -    st->mjpeg_cinfo.do_block_smoothing = FALSE;
> -    st->mjpeg_cinfo.dither_mode = JDITHER_ORDERED;
> +    decoder->mjpeg_cinfo.dct_method = JDCT_IFAST;
> +    decoder->mjpeg_cinfo.do_fancy_upsampling = FALSE;
> +    decoder->mjpeg_cinfo.do_block_smoothing = FALSE;
> +    decoder->mjpeg_cinfo.dither_mode = JDITHER_ORDERED;
>  #endif
>      // TODO: in theory should check cinfo.output_height match with our height
> -    jpeg_start_decompress(&st->mjpeg_cinfo);
> +    jpeg_start_decompress(&decoder->mjpeg_cinfo);
>      /* rec_outbuf_height is the recommended size of the output buffer we
>       * pass to libjpeg for optimum performance
>       */
> -    if (st->mjpeg_cinfo.rec_outbuf_height > G_N_ELEMENTS(lines)) {
> -        jpeg_abort_decompress(&st->mjpeg_cinfo);
> -        g_return_if_reached();
> +    if (decoder->mjpeg_cinfo.rec_outbuf_height > G_N_ELEMENTS(lines)) {
> +        jpeg_abort_decompress(&decoder->mjpeg_cinfo);
> +        g_return_val_if_reached(NULL);
>      }
>  
> -    while (st->mjpeg_cinfo.output_scanline < st->mjpeg_cinfo.output_height) {
> +    while (decoder->mjpeg_cinfo.output_scanline < decoder->mjpeg_cinfo.output_height) {
>          /* only used when JCS_EXTENSIONS is undefined */
>          G_GNUC_UNUSED unsigned int lines_read;
>  
> -        for (unsigned int j = 0; j < st->mjpeg_cinfo.rec_outbuf_height; j++) {
> +        for (unsigned int j = 0; j < decoder->mjpeg_cinfo.rec_outbuf_height; j++) {
>              lines[j] = dest;
>  #ifdef JCS_EXTENSIONS
>              dest += 4 * width;
> @@ -118,8 +136,8 @@ void stream_mjpeg_data(display_stream *st)
>              dest += 3 * width;
>  #endif
>          }
> -        lines_read = jpeg_read_scanlines(&st->mjpeg_cinfo, lines,
> -                                st->mjpeg_cinfo.rec_outbuf_height);
> +        lines_read = jpeg_read_scanlines(&decoder->mjpeg_cinfo, lines,
> +                                decoder->mjpeg_cinfo.rec_outbuf_height);
>  #ifndef JCS_EXTENSIONS
>          {
>              uint8_t *s = lines[0];
> @@ -142,15 +160,45 @@ void stream_mjpeg_data(display_stream *st)
>              }
>          }
>  #endif
> -        dest = &st->out_frame[st->mjpeg_cinfo.output_scanline * width * 4];
> +        dest = &(decoder->out_frame[decoder->mjpeg_cinfo.output_scanline * width * 4]);
>      }
> -    jpeg_finish_decompress(&st->mjpeg_cinfo);
> +    jpeg_finish_decompress(&decoder->mjpeg_cinfo);
> +
> +    return decoder->out_frame;
> +}
> +
> +static void mjpeg_decoder_destroy(MJpegDecoder* decoder)
> +{
> +    jpeg_destroy_decompress(&decoder->mjpeg_cinfo);
> +    if (decoder->out_frame) {
> +        free(decoder->out_frame);
> +    }

Can be just free(decoder->out_frame);

> +    free(decoder);
>  }
>  
>  G_GNUC_INTERNAL
> -void stream_mjpeg_cleanup(display_stream *st)
> +MJpegDecoder* create_mjpeg_decoder(int codec_type, display_stream *stream)
>  {
> -    jpeg_destroy_decompress(&st->mjpeg_cinfo);
> -    g_free(st->out_frame);
> -    st->out_frame = NULL;
> +    spice_assert(codec_type == SPICE_VIDEO_CODEC_TYPE_MJPEG);

g_return_if_fail(codec_type == SPICE_VIDEO_CODEC_TYPE_MJPEG, NULL);
would be nicer.

> +
> +    MJpegDecoder *decoder = spice_new0(MJpegDecoder, 1);
> +
> +    decoder->base.destroy = &mjpeg_decoder_destroy;
> +    decoder->base.decode_frame = &mjpeg_decoder_decode_frame;
> +    decoder->base.codec_type = codec_type;
> +    decoder->base.stream = stream;

I'd personally do

VideoDecoder *base_decoder = (VideoDecoder *)decoder;
base_decoder->destroy = ...

but that's me, I'm fine with the way you did it too.

> +
> +    decoder->mjpeg_cinfo.err = jpeg_std_error(&decoder->mjpeg_jerr);
> +    jpeg_create_decompress(&decoder->mjpeg_cinfo);
> +
> +    decoder->mjpeg_src.init_source         = mjpeg_src_init;
> +    decoder->mjpeg_src.fill_input_buffer   = mjpeg_src_fill;
> +    decoder->mjpeg_src.skip_input_data     = mjpeg_src_skip;
> +    decoder->mjpeg_src.resync_to_restart   = jpeg_resync_to_restart;
> +    decoder->mjpeg_src.term_source         = mjpeg_src_term;
> +    decoder->mjpeg_cinfo.src               = &decoder->mjpeg_src;
> +
> +    /* All the other fields are initialized to zero by spice_new0(). */
> +
> +    return decoder;
>  }
> diff --git a/src/channel-display-priv.h b/src/channel-display-priv.h
> index 71f5d17..a01183b 100644
> --- a/src/channel-display-priv.h
> +++ b/src/channel-display-priv.h
> @@ -34,6 +34,43 @@
>  
>  G_BEGIN_DECLS
>  
> +typedef struct display_stream display_stream;
> +
> +typedef struct VideoDecoder VideoDecoder;
> +#ifndef VIDEO_DECODER_T
> +# define VIDEO_DECODER_T VideoDecoder
> +#endif
> +
> +struct VideoDecoder {
> +    /* Releases the video decoder's resources */
> +    void (*destroy)(VIDEO_DECODER_T *decoder);
> +
> +    /* Decompresses the specified frame.
> +     *
> +     * @decoder:   The video decoder.
> +     * @frame_msg: The Spice message containing the compressed frame.
> +     * @return:    A pointer to the buffer holding the decoded frame. This
> +     *             buffer will be invalidated by the next call to
> +     *             decode_frame().
> +     */
> +    uint8_t* (*decode_frame)(VIDEO_DECODER_T *decoder, SpiceMsgIn *frame_msg);
> +
> +    /* The format of the encoded video. */
> +    int codec_type;
> +
> +    /* The associated display stream. */
> +    display_stream *stream;
> +};
> +
> +
> +/* Instantiates the video decoder for the specified codec.
> + *
> + * @codec_type: The format of the video.
> + * @stream:     The associated video stream.
> + * @return:     A pointer to a structure implementing the VideoDecoder methods.
> + */
> +VIDEO_DECODER_T* create_mjpeg_decoder(int codec_type, display_stream *stream);
> +
>  
>  typedef struct display_surface {
>      guint32                     surface_id;
> @@ -54,7 +91,7 @@ typedef struct drops_sequence_stats {
>      uint32_t duration;
>  } drops_sequence_stats;
>  
> -typedef struct display_stream {
> +struct display_stream {
>      SpiceMsgIn                  *msg_create;
>      SpiceMsgIn                  *msg_clip;
>      SpiceMsgIn                  *msg_data;
> @@ -64,14 +101,9 @@ typedef struct display_stream {
>      SpiceClip                   *clip;
>      QRegion                     region;
>      int                         have_region;
> -    int                         codec;
>  
> -    /* mjpeg decoder */
> -    struct jpeg_source_mgr         mjpeg_src;
> -    struct jpeg_decompress_struct  mjpeg_cinfo;
> -    struct jpeg_error_mgr          mjpeg_jerr;
> +    VideoDecoder                *video_decoder;
>  
> -    uint8_t                     *out_frame;
>      GQueue                      *msgq;
>      guint                       timeout;
>      SpiceChannel                *channel;
> @@ -98,15 +130,11 @@ typedef struct display_stream {
>      uint32_t report_num_frames;
>      uint32_t report_num_drops;
>      uint32_t report_drops_seq_len;
> -} display_stream;
> +};
>  
> -void stream_get_dimensions(display_stream *st, int *width, int *height);
> -uint32_t stream_get_current_frame(display_stream *st, uint8_t **data);
> +void stream_get_dimensions(display_stream *st, SpiceMsgIn *frame_msg, int *width, int *height);
> +uint32_t spice_msg_in_frame_data(SpiceMsgIn *frame_msg, uint8_t **data);
>  
> -/* channel-display-mjpeg.c */
> -void stream_mjpeg_init(display_stream *st);
> -void stream_mjpeg_data(display_stream *st);
> -void stream_mjpeg_cleanup(display_stream *st);
>  
>  G_END_DECLS
>  
> diff --git a/src/channel-display.c b/src/channel-display.c
> index a65f926..4033b2f 100644
> --- a/src/channel-display.c
> +++ b/src/channel-display.c
> @@ -996,7 +996,6 @@ static void display_handle_stream_create(SpiceChannel *channel, SpiceMsgIn *in)
>      st->msg_create = in;
>      spice_msg_in_ref(in);
>      st->clip = &op->clip;
> -    st->codec = op->codec_type;
>      st->surface = find_surface(c, op->surface_id);
>      st->msgq = g_queue_new();
>      st->channel = channel;
> @@ -1005,10 +1004,15 @@ static void display_handle_stream_create(SpiceChannel *channel, SpiceMsgIn *in)
>      region_init(&st->region);
>      display_update_stream_region(st);
>  
> -    switch (st->codec) {
> +    switch (op->codec_type) {
>      case SPICE_VIDEO_CODEC_TYPE_MJPEG:
> -        stream_mjpeg_init(st);
> +        st->video_decoder = create_mjpeg_decoder(op->codec_type, st);
>          break;
> +    default:
> +        st->video_decoder = NULL;
> +    }
> +    if (st->video_decoder == NULL) {
> +        spice_printerr("could not create a video decoder for codec %d", op->codec_type);
>      }
>  }
>  
> @@ -1051,15 +1055,15 @@ static gboolean display_stream_schedule(display_stream *st)
>      return FALSE;
>  }
>  
> -static SpiceRect *stream_get_dest(display_stream *st)
> +static SpiceRect *stream_get_dest(display_stream *st, SpiceMsgIn *frame_msg)
>  {
> -    if (st->msg_data == NULL ||
> -        spice_msg_in_type(st->msg_data) != SPICE_MSG_DISPLAY_STREAM_DATA_SIZED) {
> +    if (frame_msg == NULL ||
> +        spice_msg_in_type(frame_msg) != SPICE_MSG_DISPLAY_STREAM_DATA_SIZED) {
>          SpiceMsgDisplayStreamCreate *info = spice_msg_in_parsed(st->msg_create);
>  
>          return &info->dest;
>      } else {
> -        SpiceMsgDisplayStreamDataSized *op = spice_msg_in_parsed(st->msg_data);
> +        SpiceMsgDisplayStreamDataSized *op = spice_msg_in_parsed(frame_msg);
>  
>          return &op->dest;
>     }
> @@ -1074,22 +1078,17 @@ static uint32_t stream_get_flags(display_stream *st)
>  }
>  
>  G_GNUC_INTERNAL
> -uint32_t stream_get_current_frame(display_stream *st, uint8_t **data)
> +uint32_t spice_msg_in_frame_data(SpiceMsgIn *frame_msg, uint8_t **data)
>  {
> -    if (st->msg_data == NULL) {
> -        *data = NULL;
> -        return 0;
> -    }
> -
> -    if (spice_msg_in_type(st->msg_data) == SPICE_MSG_DISPLAY_STREAM_DATA) {
> -        SpiceMsgDisplayStreamData *op = spice_msg_in_parsed(st->msg_data);
> +    if (spice_msg_in_type(frame_msg) == SPICE_MSG_DISPLAY_STREAM_DATA) {
> +        SpiceMsgDisplayStreamData *op = spice_msg_in_parsed(frame_msg);
>  
>          *data = op->data;
>          return op->data_size;
>      } else {
> -        SpiceMsgDisplayStreamDataSized *op = spice_msg_in_parsed(st->msg_data);
> +        SpiceMsgDisplayStreamDataSized *op = spice_msg_in_parsed(frame_msg);
>  
> -        g_return_val_if_fail(spice_msg_in_type(st->msg_data) ==
> +        g_return_val_if_fail(spice_msg_in_type(frame_msg) ==
>                               SPICE_MSG_DISPLAY_STREAM_DATA_SIZED, 0);
>          *data = op->data;
>          return op->data_size;
> @@ -1098,19 +1097,19 @@ uint32_t stream_get_current_frame(display_stream *st, uint8_t **data)
>  }
>  
>  G_GNUC_INTERNAL
> -void stream_get_dimensions(display_stream *st, int *width, int *height)
> +void stream_get_dimensions(display_stream *st, SpiceMsgIn *frame_msg, int *width, int *height)
>  {
>      g_return_if_fail(width != NULL);
>      g_return_if_fail(height != NULL);
>  
> -    if (st->msg_data == NULL ||
> -        spice_msg_in_type(st->msg_data) != SPICE_MSG_DISPLAY_STREAM_DATA_SIZED) {
> +    if (frame_msg == NULL ||
> +        spice_msg_in_type(frame_msg) != SPICE_MSG_DISPLAY_STREAM_DATA_SIZED) {
>          SpiceMsgDisplayStreamCreate *info = spice_msg_in_parsed(st->msg_create);
>  
>          *width = info->stream_width;
>          *height = info->stream_height;
>      } else {
> -        SpiceMsgDisplayStreamDataSized *op = spice_msg_in_parsed(st->msg_data);
> +        SpiceMsgDisplayStreamDataSized *op = spice_msg_in_parsed(frame_msg);
>  
>          *width = op->width;
>          *height = op->height;
> @@ -1128,24 +1127,21 @@ static gboolean display_stream_render(display_stream *st)
>  
>          g_return_val_if_fail(in != NULL, FALSE);
>  
> -        st->msg_data = in;

Not very clear in this commit why you needed to stop storing the message
within the display_stream structure, and makes the diff bigger than it
could, I guess I'll find an explanation when looking at the commits
introducing gstreamer ;)

Looks good otherwise.

Christophe

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