[FFmpeg-devel] [PATCH 1/7] avcodec/iff: Split extract_header into extradata and packet part
Andreas Rheinhardt
andreas.rheinhardt at outlook.com
Thu Sep 15 03:52:25 EEST 2022
Andreas Rheinhardt:
> 183132872a1d8bc8a32e7fd8f994fa2f1b2d6bfc made the iff demuxer
> output extradata and made the decoder parse said extradata.
> To make this extradata extensible, it came with its own internal
> length field (containing the offset of the palette at the end
> of the extradata). Furthermore, in order to support mid-stream
> extradata changes, the packets returned by the demuxer also have
> such a length field (containing the offset of the actual packet
> data). Therefore the packet parsing the extradata accepted its
> input from both AVPackets as well as from ordinary extradata.
>
> Yet the demuxer never made use of this "feature": The packet's
> length field always indicated that the packet data starts
> immediately after the length field.
>
> Later, commit cb928fc448f9566e6f6c28d53fa4c2388e732a2b stopped
> appending the length field to the packets' data; of course,
> it also stopped searching for extradata in this data.
>
> Instead it added code to parse the packet's header to the function
> that parses extradata. This made this function consist of two disjoint
> parts, one of which is only reachable if this function is called
> from init (when parsing extradata) and one of which is reachable
> when parsing packet headers.
>
> Therefore this commit splits this function into two.
>
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at outlook.com>
> ---
> Btw: Both of these commits broke API/ABI.
>
> libavcodec/iff.c | 116 +++++++++++++++++++++++++----------------------
> 1 file changed, 61 insertions(+), 55 deletions(-)
>
> diff --git a/libavcodec/iff.c b/libavcodec/iff.c
> index 74ebddc621..4abbed8dfb 100644
> --- a/libavcodec/iff.c
> +++ b/libavcodec/iff.c
> @@ -199,11 +199,9 @@ static int cmap_read_palette(AVCodecContext *avctx, uint32_t *pal)
> * decoder structures.
> *
> * @param avctx the AVCodecContext where to extract extra context to
> - * @param avpkt the AVPacket to extract extra context from or NULL to use avctx
> * @return >= 0 in case of success, a negative error code otherwise
> */
> -static int extract_header(AVCodecContext *const avctx,
> - const AVPacket *const avpkt)
> +static int extract_header(AVCodecContext *const avctx)
> {
> IffContext *s = avctx->priv_data;
> const uint8_t *buf;
> @@ -216,55 +214,6 @@ static int extract_header(AVCodecContext *const avctx,
> }
> palette_size = avctx->extradata_size - AV_RB16(avctx->extradata);
>
> - if (avpkt && avctx->codec_tag == MKTAG('A', 'N', 'I', 'M')) {
> - uint32_t chunk_id;
> - uint64_t data_size;
> - GetByteContext *gb = &s->gb;
> -
> - bytestream2_skip(gb, 4);
> - while (bytestream2_get_bytes_left(gb) >= 1) {
> - chunk_id = bytestream2_get_le32(gb);
> - data_size = bytestream2_get_be32(gb);
> -
> - if (chunk_id == MKTAG('B', 'M', 'H', 'D')) {
> - bytestream2_skip(gb, data_size + (data_size & 1));
> - } else if (chunk_id == MKTAG('A', 'N', 'H', 'D')) {
> - unsigned extra;
> - if (data_size < 40)
> - return AVERROR_INVALIDDATA;
> -
> - s->compression = (bytestream2_get_byte(gb) << 8) | (s->compression & 0xFF);
> - bytestream2_skip(gb, 19);
> - extra = bytestream2_get_be32(gb);
> - s->is_short = !(extra & 1);
> - s->is_brush = extra == 2;
> - s->is_interlaced = !!(extra & 0x40);
> - data_size -= 24;
> - bytestream2_skip(gb, data_size + (data_size & 1));
> - } else if (chunk_id == MKTAG('D', 'L', 'T', 'A') ||
> - chunk_id == MKTAG('B', 'O', 'D', 'Y')) {
> - if (chunk_id == MKTAG('B','O','D','Y'))
> - s->compression &= 0xFF;
> - break;
> - } else if (chunk_id == MKTAG('C', 'M', 'A', 'P')) {
> - int count = data_size / 3;
> - uint32_t *pal = s->pal;
> -
> - if (count > 256)
> - return AVERROR_INVALIDDATA;
> - if (s->ham) {
> - for (i = 0; i < count; i++)
> - pal[i] = 0xFF000000 | bytestream2_get_le24(gb);
> - } else {
> - for (i = 0; i < count; i++)
> - pal[i] = 0xFF000000 | bytestream2_get_be24(gb);
> - }
> - bytestream2_skip(gb, data_size & 1);
> - } else {
> - bytestream2_skip(gb, data_size + (data_size&1));
> - }
> - }
> - } else if (!avpkt) {
> buf = avctx->extradata;
> buf_size = bytestream_get_be16(&buf);
> if (buf_size <= 1 || palette_size < 0) {
> @@ -273,7 +222,6 @@ static int extract_header(AVCodecContext *const avctx,
> buf_size, palette_size);
> return AVERROR_INVALIDDATA;
> }
> - }
>
> if (buf_size >= 41) {
> s->compression = bytestream_get_byte(&buf);
> @@ -449,7 +397,7 @@ static av_cold int decode_init(AVCodecContext *avctx)
> return AVERROR(ENOMEM);
> }
>
> - if ((err = extract_header(avctx, NULL)) < 0)
> + if ((err = extract_header(avctx)) < 0)
> return err;
>
> return 0;
> @@ -1525,6 +1473,64 @@ static int unsupported(AVCodecContext *avctx)
> return AVERROR_INVALIDDATA;
> }
>
> +static int parse_packet_header(AVCodecContext *const avctx,
> + GetByteContext *gb)
> +{
> + IffContext *s = avctx->priv_data;
> + int i;
> +
> + if (avctx->codec_tag == MKTAG('A', 'N', 'I', 'M')) {
> + uint32_t chunk_id;
> + uint64_t data_size;
> +
> + bytestream2_skip(gb, 4);
> + while (bytestream2_get_bytes_left(gb) >= 1) {
> + chunk_id = bytestream2_get_le32(gb);
> + data_size = bytestream2_get_be32(gb);
> +
> + if (chunk_id == MKTAG('B', 'M', 'H', 'D')) {
> + bytestream2_skip(gb, data_size + (data_size & 1));
> + } else if (chunk_id == MKTAG('A', 'N', 'H', 'D')) {
> + unsigned extra;
> + if (data_size < 40)
> + return AVERROR_INVALIDDATA;
> +
> + s->compression = (bytestream2_get_byte(gb) << 8) | (s->compression & 0xFF);
> + bytestream2_skip(gb, 19);
> + extra = bytestream2_get_be32(gb);
> + s->is_short = !(extra & 1);
> + s->is_brush = extra == 2;
> + s->is_interlaced = !!(extra & 0x40);
> + data_size -= 24;
> + bytestream2_skip(gb, data_size + (data_size & 1));
> + } else if (chunk_id == MKTAG('D', 'L', 'T', 'A') ||
> + chunk_id == MKTAG('B', 'O', 'D', 'Y')) {
> + if (chunk_id == MKTAG('B','O','D','Y'))
> + s->compression &= 0xFF;
> + break;
> + } else if (chunk_id == MKTAG('C', 'M', 'A', 'P')) {
> + int count = data_size / 3;
> + uint32_t *pal = s->pal;
> +
> + if (count > 256)
> + return AVERROR_INVALIDDATA;
> + if (s->ham) {
> + for (i = 0; i < count; i++)
> + pal[i] = 0xFF000000 | bytestream2_get_le24(gb);
> + } else {
> + for (i = 0; i < count; i++)
> + pal[i] = 0xFF000000 | bytestream2_get_be24(gb);
> + }
> + bytestream2_skip(gb, data_size & 1);
> + } else {
> + bytestream2_skip(gb, data_size + (data_size&1));
> + }
> + }
> + }
> +
> + return 0;
> +}
> +
> static int decode_frame(AVCodecContext *avctx, AVFrame *frame,
> int *got_frame, AVPacket *avpkt)
> {
> @@ -1538,7 +1544,7 @@ static int decode_frame(AVCodecContext *avctx, AVFrame *frame,
>
> bytestream2_init(gb, avpkt->data, avpkt->size);
>
> - if ((res = extract_header(avctx, avpkt)) < 0)
> + if ((res = parse_packet_header(avctx, gb)) < 0)
> return res;
>
> if ((res = ff_get_buffer(avctx, frame, 0)) < 0)
Will apply this patchset tonight unless there are objections.
- Andreas
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