vp8: WebP decoding support

VP8L, padding and bounds checks by Pascal Massimino

Reviewed-by: Pascal Massimino <pascal.massimino@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

1 files changed, 61 insertions, 0 deletions

diff --git a/libavcodec/vp8.c b/libavcodec/vp8.c
index ac929d03b4..1ab76b5278 100644
--- a/libavcodec/vp8.c
+++ b/libavcodec/vp8.c
@@ -2094,6 +2094,52 @@ static int vp8_decode_update_thread_context(AVCodecContext *dst, const AVCodecCo
     return 0;
 }
 
+static unsigned apply_padding(unsigned size) { return size + (size & 1); }
+
+static int webp_decode_frame(AVCodecContext *avctx, void *data, int *data_size,
+                             AVPacket *avpkt)
+{
+    const uint8_t *buf = avpkt->data;
+    int buf_size       = avpkt->size;
+    AVPacket pkt       = *avpkt;
+
+    if (buf_size >= 16
+        && AV_RL32(buf   ) == AV_RL32("RIFF")
+        && AV_RL32(buf+ 8) == AV_RL32("WEBP")) {
+        unsigned riff_size = apply_padding(AV_RL32(buf+4)) + 8;
+        buf += 12;   // Skip over main header
+        buf_size -= 12;
+        if (buf_size < 8 || riff_size < 8) {
+            av_log(avctx, AV_LOG_ERROR, "Incomplete header.\n");
+            return AVERROR_INVALIDDATA;
+        }
+        if (AV_RL32(buf) == AV_RL32("VP8L")) {
+            av_log(avctx, AV_LOG_ERROR, "Unsupported WebP lossless format.\n");
+            return AVERROR_PATCHWELCOME;
+        }
+        if (AV_RL32(buf) == AV_RL32("VP8X") && AV_RL32(buf+4) < (unsigned)buf_size) {
+            unsigned size = apply_padding(AV_RL32(buf+4) + 8);
+            buf      += size;
+            buf_size -= size;
+        }
+        if (buf_size >= 8
+            && AV_RL32(buf) == AV_RL32("ALPH") && AV_RL32(buf+4) < (unsigned)buf_size) {
+            unsigned size = apply_padding(AV_RL32(buf+4) + 8);
+            buf      += size;
+            buf_size -= size;
+            av_log(avctx, AV_LOG_WARNING, "Skipping alpha plane\n");
+        }
+        if (buf_size >= 8 && AV_RL32(buf) == AV_RL32("VP8 ")) {
+            buf      += 8;
+            buf_size -= 8;
+        }
+    }
+    pkt.data = buf;
+    pkt.size = buf_size;
+
+    return vp8_decode_frame(avctx, data, data_size, &pkt);
+}
+
 AVCodec ff_vp8_decoder = {
     .name                  = "vp8",
     .type                  = AVMEDIA_TYPE_VIDEO,
@@ -2108,3 +2154,18 @@ AVCodec ff_vp8_decoder = {
     .init_thread_copy      = ONLY_IF_THREADS_ENABLED(vp8_decode_init_thread_copy),
     .update_thread_context = ONLY_IF_THREADS_ENABLED(vp8_decode_update_thread_context),
 };
+
+AVCodec ff_webp_decoder = {
+    .name                  = "webp",
+    .type                  = AVMEDIA_TYPE_VIDEO,
+    .id                    = AV_CODEC_ID_WEBP,
+    .priv_data_size        = sizeof(VP8Context),
+    .init                  = vp8_decode_init,
+    .close                 = vp8_decode_free,
+    .decode                = webp_decode_frame,
+    .capabilities          = CODEC_CAP_DR1 | CODEC_CAP_FRAME_THREADS | CODEC_CAP_SLICE_THREADS,
+    .flush                 = vp8_decode_flush,
+    .long_name             = NULL_IF_CONFIG_SMALL("WebP"),
+    .init_thread_copy      = ONLY_IF_THREADS_ENABLED(vp8_decode_init_thread_copy),
+    .update_thread_context = ONLY_IF_THREADS_ENABLED(vp8_decode_update_thread_context),
+};