Jan 2, 2023, 13:53 by d.kozin...@samsung.com:
> - Added constants definitions for EVC parser
> - Provided NAL units parsing following ISO_IEC_23094-1
> - EVC parser registration
>
> Signed-off-by: Dawid Kozinski <d.kozin...@samsung.com>
> ---
> libavcodec/Makefile | 1 +
> libavcodec/evc.h | 155 +++++
> libavcodec/evc_parser.c | 1417 +++++++++++++++++++++++++++++++++++++++
> libavcodec/parsers.c | 1 +
> 4 files changed, 1574 insertions(+)
> create mode 100644 libavcodec/evc.h
> create mode 100644 libavcodec/evc_parser.c
>
>
> +
> +// @see ISO_IEC_23094-1 (7.3.7 Reference picture list structure syntax)
> +static int ref_pic_list_struct(GetBitContext* gb, RefPicListStruct* rpl)
> +{
> + uint32_t delta_poc_st, strp_entry_sign_flag = 0;
> + rpl->ref_pic_num = get_ue_golomb(gb);
> + if (rpl->ref_pic_num > 0)
> + {
> + delta_poc_st = get_ue_golomb(gb);
> +
> + rpl->ref_pics[0] = delta_poc_st;
> + if (rpl->ref_pics[0] != 0)
> + {
> + strp_entry_sign_flag = get_bits(gb, 1);
> +
> + rpl->ref_pics[0] *= 1 - (strp_entry_sign_flag << 1);
> + }
> + }
> +
> + for (int i = 1; i < rpl->ref_pic_num; ++i)
> + {
> + delta_poc_st = get_ue_golomb(gb);
> + if (delta_poc_st != 0) {
> + strp_entry_sign_flag = get_bits(gb, 1);
> + }
> + rpl->ref_pics[i] = rpl->ref_pics[i - 1] + delta_poc_st * (1 -
> (strp_entry_sign_flag << 1));
> + }
> +
> + return 0;
> +}
>
Code style issues here, we don't put a newline on the bracket
after an if or a for, and we don't use brackets at all for one-line
if statements or if/else statements (as long as all statements are one-line).
> +/**
> + * @brief Reconstruct NAL Unit from incomplete data
> + *
> + * @param[in] s parser context
> + * @param[in] data pointer to the buffer containg new data for current NALU
> prefix
> + * @param[in] data_size amount of bytes to read from the input buffer
> + * @param[out] nalu_prefix assembled NALU length
> + * @param[in ] avctx codec context
> + *
> + * Assemble the NALU prefix storing NALU length if it has been split between
> 2 subsequent buffers (input chunks) incoming to the parser.
> + * This is the case when the buffer size is not enough for the buffer to
> store the whole NAL unit prefix.
> + * In this case, we have to get part of the prefix from the previous buffer
> and assemble it with the rest from the current buffer.
> + * Then we'll be able to read NAL unit size.
> + */
> +static int evc_assemble_nalu_prefix(AVCodecParserContext *s, const uint8_t
> *data, int data_size,
> + uint8_t *nalu_prefix, AVCodecContext
> *avctx)
> +{
> + EVCParserContext *ctx = s->priv_data;
> + ParseContext *pc = &ctx->pc;
> +
> + // 1. pc->buffer contains previously read bytes of NALU prefix
> + // 2. buf contains the rest of NAL unit prefix bytes
> + //
> + // ~~~~~~~
> + // EXAMPLE
> + // ~~~~~~~
> + //
> + // In the following example we assumed that the number of already read
> NAL Unit prefix bytes is equal 1
> + //
> + // ----------
> + // pc->buffer -> conatins already read bytes
> + // ----------
> + // __ pc->index == 1
> + // |
> + // V
> + // -------------------------------------------------------
> + // | 0 | 1 | 2 | 3 | 4 | ... | N |
> + // -------------------------------------------------------
> + // | 0x00 | 0xXX | 0xXX | 0xXX | 0xXX | ... | 0xXX |
> + // -------------------------------------------------------
> + // | PREF | | | | | ... | |
> + // -------------------------------------------------------
> + //
> + // ----------
> + // buf -> contains newly read bytes
> + // ----------
> + // -------------------------------------------------------
> + // | 0 | 1 | 2 | 3 | 4 | ... | N |
> + // -------------------------------------------------------
> + // | 0x00 | 0x00 | 0x3C | 0xXX | 0xXX | ... | 0xXX |
> + // -------------------------------------------------------
> + // | PREF | PREF | PREF | | | ... | |
> + // -------------------------------------------------------
> + //
> + // ----------
> + // nalu_prefix
> + // ----------
> + // ---------------------------------
> + // | 0 | 1 | 2 | 3 |
> + // ---------------------------------
> + // | 0x00 | 0x00 | 0x00 | 0x3C |
> + // ---------------------------------
> + // | NALU LENGTH |
> + // ---------------------------------
> + // NAL Unit lenght = 60 (0x0000003C)
> + //
>
The ascii art is neat, but it just makes this more complicated to read,
and it doesn't even say all that much about it. just remove it.
> + for (int i = 0; i < EVC_NALU_LENGTH_PREFIX_SIZE; i++) {
> + if (i < pc->index)
> + nalu_prefix[i] = pc->buffer[i];
> + else
> + nalu_prefix[i] = data[i - pc->index];
> + }
> +
> + return 0;
> +}
> +
> +/**
> + * @brief Reconstruct NALU from incomplete data
> + * Assemble NALU if it is split between multiple buffers
> + *
> + * This is the case when buffer size is not enough for the buffer to store
> NAL unit.
> + * In this case, we have to get parts of the NALU from the previous buffers
> stored in pc->buffer and assemble it with the rest from the current buffer.
> + *
> + * @param[in] s parser context
> + * @param[in] data pointer to the buffer containg new data for current NALU
> + * @param[in] data_size amount of bytes to read from the input buffer
> + * @param[out] nalu pointer to the memory block for storing assembled NALU
> + * @param[in] nalu_size assembled NALU length
> + * @param[in ] avctx codec context
> + */
>
You really don't need to put doxy on every single function, only for those
that are not immediately self-explanatory, and you don't even need to
use a doxy syntax for those, just a one or two-line comment on what
it does, if it's not obvious.
Rest of the code looks fine.
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