Quoting Paul B Mahol (2023-01-31 11:18:52)
> Patch attached.
>
> From c9ec824211cccb745b3a4ab014d6be726c8ef1b9 Mon Sep 17 00:00:00 2001
> From: Paul B Mahol <one...@gmail.com>
> Date: Tue, 31 Jan 2023 10:18:17 +0100
> Subject: [PATCH] avcodec: add media100_to_mjpegb bitstream filter and use it
>
> Signed-off-by: Paul B Mahol <one...@gmail.com>
> ---
> libavcodec/Makefile | 3 +-
> libavcodec/bitstream_filters.c | 1 +
> .../{media100.c => media100_to_mjpegb_bsf.c} | 112 +++++++-----------
> libavcodec/mjpegbdec.c | 15 +++
> 4 files changed, 61 insertions(+), 70 deletions(-)
> rename libavcodec/{media100.c => media100_to_mjpegb_bsf.c} (65%)
Needs media100_decoder_select="media100_to_mjpegb_bsf" in configure and
a changelog entry.
> -static av_cold int media100_decode_init(AVCodecContext *avctx)
> +static av_cold int init(AVBSFContext *ctx)
> {
> - Media100Context *ctx = avctx->priv_data;
> - const AVCodec *codec;
> - int ret;
> -
> - codec = avcodec_find_decoder(AV_CODEC_ID_MJPEGB);
> - if (!codec)
> - return AVERROR_BUG;
> - ctx->avctx = avcodec_alloc_context3(codec);
> - if (!ctx->avctx)
> - return AVERROR(ENOMEM);
> - ctx->avctx->thread_count = 1;
> - ctx->avctx->flags = avctx->flags;
> - ctx->avctx->flags2 = avctx->flags2;
> - ctx->avctx->width = ctx->avctx->coded_width = avctx->width;
> - ctx->avctx->height = ctx->avctx->coded_height = avctx->height;
> -
> - ret = avcodec_open2(ctx->avctx, codec, NULL);
> - if (ret < 0)
> - return ret;
> + Media100Context *s = ctx->priv_data;
>
> - ctx->pkt = av_packet_alloc();
> - if (!ctx->pkt)
> + s->pkt = av_packet_alloc();
> + if (!s->pkt)
> return AVERROR(ENOMEM);
Should set ctx->par_out->codec_id to AV_CODEC_ID_MJPEGB, so people can
use this bsf standalone.
>
> return 0;
> }
>
> -static int media100_decode_frame(AVCodecContext *avctx,
> - AVFrame *frame, int *got_frame,
> - AVPacket *avpkt)
> +static int filter(AVBSFContext *ctx, AVPacket *avpkt)
> {
> - Media100Context *ctx = avctx->priv_data;
> + Media100Context *s = ctx->priv_data;
> unsigned second_field_offset = 0;
> unsigned next_field = 0;
> unsigned dht_offset[2];
> @@ -83,18 +62,20 @@ static int media100_decode_frame(AVCodecContext *avctx,
> AVPacket *pkt;
> int ret;
>
> - if (avpkt->size + 1024 > ctx->pkt->size) {
> - ret = av_grow_packet(ctx->pkt, avpkt->size + 1024 - ctx->pkt->size);
> - if (ret < 0)
> - return ret;
> - }
> + ret = ff_bsf_get_packet_ref(ctx, avpkt);
> + if (ret < 0)
> + return ret;
>
> - ret = av_packet_make_writable(ctx->pkt);
> + ret = av_new_packet(s->pkt, avpkt->size + 1024);
> + if (ret < 0)
> + return ret;
> +
> + ret = av_packet_make_writable(s->pkt);
> if (ret < 0)
> return ret;
>
> bytestream2_init(&gb, avpkt->data, avpkt->size);
> - bytestream2_init_writer(&pb, ctx->pkt->data, ctx->pkt->size);
> + bytestream2_init_writer(&pb, s->pkt->data, s->pkt->size);
>
> second_field:
> bytestream2_put_be32(&pb, 0);
> @@ -107,8 +88,8 @@ second_field:
> sof_offset[field] = bytestream2_tell_p(&pb);
> bytestream2_put_be16(&pb, 17);
> bytestream2_put_byte(&pb, 8);
> - bytestream2_put_be16(&pb, avctx->height / 2);
> - bytestream2_put_be16(&pb, avctx->width);
> + bytestream2_put_be16(&pb, ctx->par_in->height / 2);
> + bytestream2_put_be16(&pb, ctx->par_in->width);
> bytestream2_put_byte(&pb, 3);
> bytestream2_put_byte(&pb, 1);
> bytestream2_put_byte(&pb, 0x21);
> @@ -164,7 +145,7 @@ second_field:
> goto second_field;
> }
>
> - pkt = ctx->pkt;
> + pkt = s->pkt;
>
> AV_WB32(pkt->data + 8, second_field_offset);
> AV_WB32(pkt->data + 12, second_field_offset);
> @@ -186,40 +167,33 @@ second_field:
>
> pkt->size = bytestream2_tell_p(&pb);
>
> - ret = avcodec_send_packet(ctx->avctx, pkt);
> - if (ret < 0) {
> - av_log(avctx, AV_LOG_ERROR, "Error submitting a packet for
> decoding\n");
> - return ret;
> - }
> + av_packet_copy_props(pkt, avpkt);
check the return value
A FATE test would be nice.
--
Anton Khirnov
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