Re: [FFmpeg-devel] [PATCH v2 3/3] avcodec/avs2_parser: parse more info

[Andreas Rheinhardt <andreas.rheinhardt@outlook.com>]

Zhao Zhili:
> Including video resolution, framerate and picture type, etc.
> 
> Signed-off-by: Zhao Zhili <quinkblack@foxmail.com>
> ---
> v2: fix unused variable warning
> 
>  libavcodec/avs2.h        |  27 ++++++++++
>  libavcodec/avs2_parser.c | 103 +++++++++++++++++++++++++++++++++++++++
>  2 files changed, 130 insertions(+)
> 
> diff --git a/libavcodec/avs2.h b/libavcodec/avs2.h
> index f342ba52a0..e961c7d517 100644
> --- a/libavcodec/avs2.h
> +++ b/libavcodec/avs2.h
> @@ -23,6 +23,8 @@
>  #ifndef AVCODEC_AVS2_H
>  #define AVCODEC_AVS2_Hto 
>  
> +#include "libavutil/rational.h"
> +
>  #define AVS2_SLICE_MAX_START_CODE    0x000001AF
>  
>  enum {
> @@ -38,4 +40,29 @@ enum {
>  #define AVS2_ISPIC(x)  ((x) == AVS2_INTRA_PIC_START_CODE || (x) == AVS2_INTER_PIC_START_CODE)
>  #define AVS2_ISUNIT(x) ((x) == AVS2_SEQ_START_CODE || AVS2_ISPIC(x))
>  
> +enum AVS2Profile {
> +    AVS2_PROFILE_MAIN_PIC   = 0x12,
> +    AVS2_PROFILE_MAIN       = 0x20,
> +    AVS2_PROFILE_MAIN10     = 0x22,
> +};
> +
> +static const AVRational ff_avs2_frame_rate_tab[16] = {

If this is only used at one place (as it is), it should be moved to that
place; if it is to be used in several places, it should be moved to a
single file instead of a header.

> +    { 0    , 0   }, // forbid
> +    { 24000, 1001},
> +    { 24   , 1   },
> +    { 25   , 1   },
> +    { 30000, 1001},
> +    { 30   , 1   },
> +    { 50   , 1   },
> +    { 60000, 1001},
> +    { 60   , 1   },
> +    { 100  , 1   },
> +    { 120  , 1   },
> +    { 200  , 1   },
> +    { 240  , 1   },
> +    { 300  , 1   },
> +    { 0    , 0   }, // reserved
> +    { 0    , 0   }  // reserved
> +};
> +
>  #endif
> diff --git a/libavcodec/avs2_parser.c b/libavcodec/avs2_parser.c
> index 71cf442903..18d7729768 100644
> --- a/libavcodec/avs2_parser.c
> +++ b/libavcodec/avs2_parser.c
> @@ -19,7 +19,9 @@
>   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
>   */
>  
> +#include "libavutil/avutil.h"
>  #include "avs2.h"
> +#include "get_bits.h"
>  #include "parser.h"
>  
>  static int avs2_find_frame_end(ParseContext *pc, const uint8_t *buf, int buf_size)
> @@ -58,6 +60,105 @@ static int avs2_find_frame_end(ParseContext *pc, const uint8_t *buf, int buf_siz
>      return END_NOT_FOUND;
>  }
>  
> +static void parse_avs2_seq_header(AVCodecParserContext *s, const uint8_t *buf,
> +                                 int buf_size, AVCodecContext *avctx)
> +{
> +    GetBitContext gb;
> +    int profile, level;
> +    int width, height;
> +    int chroma, sample_precision, encoding_precision = 1;
> +    // sample_precision and encoding_precision is 3 bits
> +    static uint8_t precision[8] = { 0, 8, 10 };

Missing const.

> +    unsigned aspect_ratio;
> +    unsigned frame_rate_code;
> +    int low_delay;
> +
> +    if (buf_size < 15)
> +        return;
> +
> +    init_get_bits8(&gb, buf, buf_size);

If buf_size is gigantic, init_get_bits8 can fail. Given that you only
ever read the first 15 bytes of the header, you can avoid this by
initializing the GetBitContext with a size of 15.

> +
> +    s->key_frame = 1;
> +    s->pict_type = AV_PICTURE_TYPE_I;
> +
> +    profile = get_bits(&gb, 8);
> +    level = get_bits(&gb, 8);
> +
> +    // progressive_sequence     u(1)
> +    // field_coded_sequence     u(1)
> +    skip_bits(&gb, 2);
> +
> +    width = get_bits(&gb, 14);
> +    height = get_bits(&gb, 14);
> +
> +    chroma = get_bits(&gb, 2);
> +    sample_precision = get_bits(&gb, 3);
> +    if (profile == AVS2_PROFILE_MAIN10)
> +        encoding_precision = get_bits(&gb, 3);
> +
> +    aspect_ratio = get_bits(&gb, 4);
> +    frame_rate_code = get_bits(&gb, 4);
> +
> +    // bit_rate_lower       u(18)
> +    // marker_bit           f(1)
> +    // bit_rate_upper       u(12)
> +    skip_bits(&gb, 31);
> +
> +    low_delay = get_bits(&gb, 1);
> +
> +    s->width = width;
> +    s->height = height;
> +    s->coded_width = FFALIGN(width, 8);
> +    s->coded_height = FFALIGN(height, 8);
> +    avctx->framerate.num = avctx->time_base.den =
> +        ff_avs2_frame_rate_tab[frame_rate_code].num;
> +    avctx->framerate.den = avctx->time_base.num =
> +        ff_avs2_frame_rate_tab[frame_rate_code].den;
> +    avctx->has_b_frames = FFMAX(avctx->has_b_frames, !low_delay);
> +
> +    av_log(avctx, AV_LOG_DEBUG,
> +           "AVS2 parse seq HDR: profile %x, level %x, "
> +           "width %d, height %d, "
> +           "chroma %d, sample_precision %d bits, encoding_precision %d bits, "
> +           "aspect_ratio 0x%x, framerate %d/%d, low_delay %d\n",
> +           profile, level,
> +           width, height,
> +           chroma, precision[sample_precision], precision[encoding_precision],
> +           aspect_ratio, avctx->framerate.num, avctx->framerate.den, low_delay);
> +}
> +
> +static void parse_avs2_units(AVCodecParserContext *s, const uint8_t *buf,
> +                             int buf_size, AVCodecContext *avctx)
> +{
> +    if (buf_size < 5)
> +        return;
> +
> +    if (!(buf[0] == 0x0 && buf[1] == 0x0 && buf[2] == 0x1))
> +        return;
> +
> +    switch (buf[3]) {
> +    case AVS2_SEQ_START_CODE:
> +        parse_avs2_seq_header(s, buf + 4, buf_size - 4, avctx);
> +        return;
> +    case AVS2_INTRA_PIC_START_CODE:
> +        s->key_frame = 1;
> +        s->pict_type = AV_PICTURE_TYPE_I;
> +        return;
> +    case AVS2_INTER_PIC_START_CODE:
> +        s->key_frame = 0;
> +        if (buf_size > 9) {
> +            int pic_code_type = buf[8] & 0x3;
> +            if (pic_code_type == 1)
> +                s->pict_type = AV_PICTURE_TYPE_P;
> +            else if (pic_code_type == 3)
> +                s->pict_type = AV_PICTURE_TYPE_S;
> +            else
> +                s->pict_type = AV_PICTURE_TYPE_B;
> +        }
> +        return;
> +    }
> +}
> +
>  static int avs2_parse(AVCodecParserContext *s, AVCodecContext *avctx,
>                        const uint8_t **poutbuf, int *poutbuf_size,
>                        const uint8_t *buf, int buf_size)
> @@ -76,6 +177,8 @@ static int avs2_parse(AVCodecParserContext *s, AVCodecContext *avctx,
>          }
>      }
>  
> +    parse_avs2_units(s, buf, buf_size, avctx);
> +
>      *poutbuf = buf;
>      *poutbuf_size = buf_size;
>  

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