[FFmpeg-devel] [PATCH 1/5] avcodec/h264_mp4toannexb_bsf: refactor start_code_size handling

["zhilizhao(赵志立)"]

Ping for the patchset.

> On May 20, 2023, at 00:41, Zhao Zhili <quinkblack at foxmail.com> wrote:
> 
> From: Zhao Zhili <zhilizhao at tencent.com>
> 
> start_code_size depends on whether PS comes from out-of-band or
> in-band. Make the code more readable.
> ---
> libavcodec/h264_mp4toannexb_bsf.c | 34 ++++++++++++++++++++++++-------
> 1 file changed, 27 insertions(+), 7 deletions(-)
> 
> diff --git a/libavcodec/h264_mp4toannexb_bsf.c b/libavcodec/h264_mp4toannexb_bsf.c
> index d11be455c2..7dce1ae9b6 100644
> --- a/libavcodec/h264_mp4toannexb_bsf.c
> +++ b/libavcodec/h264_mp4toannexb_bsf.c
> @@ -43,10 +43,26 @@ typedef struct H264BSFContext {
>     int      extradata_parsed;
> } H264BSFContext;
> 
> +enum PsSource {
> +    PS_OUT_OF_BAND = -1,
> +    PS_NONE = 0,
> +    PS_IN_BAND = 1,
> +};
> +
> static void count_or_copy(uint8_t **out, uint64_t *out_size,
> -                          const uint8_t *in, int in_size, int ps, int copy)
> +                          const uint8_t *in, int in_size, enum PsSource ps, int copy)
> {
> -    uint8_t start_code_size = ps < 0 ? 0 : *out_size == 0 || ps ? 4 : 3;
> +    uint8_t start_code_size;
> +
> +    if (ps == PS_OUT_OF_BAND)
> +        /* start code already present in out-of-band ps data, so don't need to
> +         * add it manually again
> +         */
> +        start_code_size = 0;
> +    else if (ps == PS_IN_BAND || *out_size == 0)
> +        start_code_size = 4;
> +    else
> +        start_code_size = 3;
> 
>     if (copy) {
>         memcpy(*out + start_code_size, in, in_size);
> @@ -202,6 +218,7 @@ static int h264_mp4toannexb_filter(AVBSFContext *ctx, AVPacket *opkt)
> 
>         do {
>             uint32_t nal_size = 0;
> +            enum PsSource ps;
> 
>             /* possible overread ok due to padding */
>             for (int i = 0; i < s->length_size; i++)
> @@ -230,7 +247,7 @@ static int h264_mp4toannexb_filter(AVBSFContext *ctx, AVPacket *opkt)
>                     if (!s->sps_size) {
>                         LOG_ONCE(ctx, AV_LOG_WARNING, "SPS not present in the stream, nor in AVCC, stream may be unreadable\n");
>                     } else {
> -                        count_or_copy(&out, &out_size, s->sps, s->sps_size, -1, j);
> +                        count_or_copy(&out, &out_size, s->sps, s->sps_size, PS_OUT_OF_BAND, j);
>                         sps_seen = 1;
>                     }
>                 }
> @@ -246,19 +263,22 @@ static int h264_mp4toannexb_filter(AVBSFContext *ctx, AVPacket *opkt)
>             if (new_idr && unit_type == H264_NAL_IDR_SLICE && !sps_seen && !pps_seen) {
>                 if (ctx->par_out->extradata)
>                     count_or_copy(&out, &out_size, ctx->par_out->extradata,
> -                                  ctx->par_out->extradata_size, -1, j);
> +                                  ctx->par_out->extradata_size, PS_OUT_OF_BAND, j);
>                 new_idr = 0;
>             /* if only SPS has been seen, also insert PPS */
>             } else if (new_idr && unit_type == H264_NAL_IDR_SLICE && sps_seen && !pps_seen) {
>                 if (!s->pps_size) {
>                     LOG_ONCE(ctx, AV_LOG_WARNING, "PPS not present in the stream, nor in AVCC, stream may be unreadable\n");
>                 } else {
> -                    count_or_copy(&out, &out_size, s->pps, s->pps_size, -1, j);
> +                    count_or_copy(&out, &out_size, s->pps, s->pps_size, PS_OUT_OF_BAND, j);
>                 }
>             }
> 
> -            count_or_copy(&out, &out_size, buf, nal_size,
> -                          unit_type == H264_NAL_SPS || unit_type == H264_NAL_PPS, j);
> +            if (unit_type == H264_NAL_SPS || unit_type == H264_NAL_PPS)
> +                ps = PS_IN_BAND;
> +            else
> +                ps = PS_NONE;
> +            count_or_copy(&out, &out_size, buf, nal_size, ps, j);
>             if (!new_idr && unit_type == H264_NAL_SLICE) {
>                 new_idr  = 1;
>                 sps_seen = 0;
> -- 
> 2.25.1
> 
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel at ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> 
> To unsubscribe, visit link above, or email
> ffmpeg-devel-request at ffmpeg.org with subject "unsubscribe".