avcodec: rewrite gif muxing and encoding

Now "-c copy" works.
Update FATE files.

Demuxer only split file into packets, no data is trimmed.
Encoder & muxer currently expect completely another format
where muxer writes stuff like disposal method which should
be really encoder job.
With this patch muxer only modifies delay between two packets.
Codec copy need to have same behavior between demuxer and
muxer to work correctly.

Fixes #6640.

1 files changed, 100 insertions, 140 deletions

diff --git a/libavformat/gif.c b/libavformat/gif.c
index 62d995a907..8bfe59afe8 100644
--- a/libavformat/gif.c
+++ b/libavformat/gif.c
@@ -27,94 +27,21 @@
 #include "libavutil/imgutils.h"
 #include "libavutil/log.h"
 #include "libavutil/opt.h"
+#include "libavcodec/bytestream.h"
 #include "libavcodec/gif.h"
 
-/* XXX: random value that shouldn't be taken into effect if there is no
- * transparent color in the palette (the transparency bit will be set to 0) */
-#define DEFAULT_TRANSPARENCY_INDEX 0x1f
-
-static int get_palette_transparency_index(const uint32_t *palette)
-{
-    int transparent_color_index = -1;
-    unsigned i, smallest_alpha = 0xff;
-
-    if (!palette)
-        return -1;
-
-    for (i = 0; i < AVPALETTE_COUNT; i++) {
-        const uint32_t v = palette[i];
-        if (v >> 24 < smallest_alpha) {
-            smallest_alpha = v >> 24;
-            transparent_color_index = i;
-        }
-    }
-    return smallest_alpha < 128 ? transparent_color_index : -1;
-}
-
-static int gif_image_write_header(AVIOContext *pb, AVStream *st,
-                                  int loop_count, uint32_t *palette)
-{
-    int i;
-    int64_t aspect = 0;
-    const AVRational sar = st->sample_aspect_ratio;
-
-    if (sar.num > 0 && sar.den > 0) {
-        aspect = sar.num * 64LL / sar.den - 15;
-        if (aspect < 0 || aspect > 255)
-            aspect = 0;
-    }
-
-    avio_write(pb, gif89a_sig, sizeof(gif89a_sig));
-    avio_wl16(pb, st->codecpar->width);
-    avio_wl16(pb, st->codecpar->height);
-
-    if (palette) {
-        const int bcid = get_palette_transparency_index(palette);
-
-        avio_w8(pb, 0xf7); /* flags: global clut, 256 entries */
-        avio_w8(pb, bcid < 0 ? DEFAULT_TRANSPARENCY_INDEX : bcid); /* background color index */
-        avio_w8(pb, aspect);
-        for (i = 0; i < 256; i++) {
-            const uint32_t v = palette[i] & 0xffffff;
-            avio_wb24(pb, v);
-        }
-    } else {
-        avio_w8(pb, 0); /* flags */
-        avio_w8(pb, 0); /* background color index */
-        avio_w8(pb, aspect);
-    }
-
-
-    if (loop_count >= 0 ) {
-        /* "NETSCAPE EXTENSION" for looped animation GIF */
-        avio_w8(pb, 0x21); /* GIF Extension code */
-        avio_w8(pb, 0xff); /* Application Extension Label */
-        avio_w8(pb, 0x0b); /* Length of Application Block */
-        avio_write(pb, "NETSCAPE2.0", sizeof("NETSCAPE2.0") - 1);
-        avio_w8(pb, 0x03); /* Length of Data Sub-Block */
-        avio_w8(pb, 0x01);
-        avio_wl16(pb, (uint16_t)loop_count);
-        avio_w8(pb, 0x00); /* Data Sub-block Terminator */
-    }
-
-    avio_flush(pb);
-    return 0;
-}
-
 typedef struct GIFContext {
     AVClass *class;
     int loop;
     int last_delay;
-    AVPacket *prev_pkt;
     int duration;
+    int64_t last_pos;
+    int have_end;
+    AVPacket *prev_pkt;
 } GIFContext;
 
 static int gif_write_header(AVFormatContext *s)
 {
-    GIFContext *gif = s->priv_data;
-    AVCodecParameters *video_par;
-    uint32_t palette[AVPALETTE_COUNT];
-
     if (s->nb_streams != 1 ||
         s->streams[0]->codecpar->codec_type != AVMEDIA_TYPE_VIDEO ||
         s->streams[0]->codecpar->codec_id   != AV_CODEC_ID_GIF) {
@@ -123,92 +50,123 @@ static int gif_write_header(AVFormatContext *s)
         return AVERROR(EINVAL);
     }
 
-    video_par = s->streams[0]->codecpar;
-
     avpriv_set_pts_info(s->streams[0], 64, 1, 100);
-    if (avpriv_set_systematic_pal2(palette, video_par->format) < 0) {
-        av_assert0(video_par->format == AV_PIX_FMT_PAL8);
-        /* delay header writing: we wait for the first palette to put it
-         * globally */
-    } else {
-        gif_image_write_header(s->pb, s->streams[0], gif->loop, palette);
-    }
 
     return 0;
 }
 
-static int flush_packet(AVFormatContext *s, AVPacket *new)
+static int gif_parse_packet(AVFormatContext *s, uint8_t *data, int size)
 {
-    GIFContext *gif = s->priv_data;
-    int size, bcid;
-    AVIOContext *pb = s->pb;
-    const uint32_t *palette;
-    AVPacket *pkt = gif->prev_pkt;
-
-    if (!pkt)
-        return 0;
+    GetByteContext gb;
+    int x;
+
+    bytestream2_init(&gb, data, size);
+
+    while (bytestream2_get_bytes_left(&gb) > 0) {
+        x = bytestream2_get_byte(&gb);
+        if (x != GIF_EXTENSION_INTRODUCER)
+            return 0;
+
+        x = bytestream2_get_byte(&gb);
+        while (x != GIF_GCE_EXT_LABEL && bytestream2_get_bytes_left(&gb) > 0) {
+            int block_size = bytestream2_get_byte(&gb);
+            if (!block_size)
+                break;
+            bytestream2_skip(&gb, block_size);
+        }
 
-    /* Mark one colour as transparent if the input palette contains at least
-     * one colour that is more than 50% transparent. */
-    palette = (uint32_t*)av_packet_get_side_data(pkt, AV_PKT_DATA_PALETTE, &size);
-    if (palette && size != AVPALETTE_SIZE) {
-        av_log(s, AV_LOG_ERROR, "Invalid palette extradata\n");
-        return AVERROR_INVALIDDATA;
+        if (x == GIF_GCE_EXT_LABEL)
+            return bytestream2_tell(&gb) + 2;
     }
-    bcid = get_palette_transparency_index(palette);
 
+    return 0;
+}
+
+static int gif_get_delay(GIFContext *gif, AVPacket *prev, AVPacket *new)
+{
     if (new && new->pts != AV_NOPTS_VALUE)
-        gif->duration = av_clip_uint16(new->pts - gif->prev_pkt->pts);
+        gif->duration = av_clip_uint16(new->pts - prev->pts);
     else if (!new && gif->last_delay >= 0)
         gif->duration = gif->last_delay;
 
-    /* graphic control extension block */
-    avio_w8(pb, 0x21);
-    avio_w8(pb, 0xf9);
-    avio_w8(pb, 0x04); /* block size */
-    avio_w8(pb, 1<<2 | (bcid >= 0));
-    avio_wl16(pb, gif->duration);
-    avio_w8(pb, bcid < 0 ? DEFAULT_TRANSPARENCY_INDEX : bcid);
-    avio_w8(pb, 0x00);
-
-    avio_write(pb, pkt->data, pkt->size);
-
-    av_packet_unref(gif->prev_pkt);
-    if (new)
-        av_packet_ref(gif->prev_pkt, new);
-
-    return 0;
+    return gif->duration;
 }
 
-static int gif_write_packet(AVFormatContext *s, AVPacket *pkt)
+static int gif_write_packet(AVFormatContext *s, AVPacket *new_pkt)
 {
     GIFContext *gif = s->priv_data;
-    AVStream *video_st = s->streams[0];
+    AVIOContext *pb = s->pb;
+    AVPacket *pkt = gif->prev_pkt;
 
     if (!gif->prev_pkt) {
         gif->prev_pkt = av_packet_alloc();
         if (!gif->prev_pkt)
             return AVERROR(ENOMEM);
+        return av_packet_ref(gif->prev_pkt, new_pkt);
+    }
+
+    gif->last_pos = avio_tell(pb);
+    if (pkt->size > 0)
+        gif->have_end = pkt->data[pkt->size - 1] == GIF_TRAILER;
 
-        /* Write the first palette as global palette */
-        if (video_st->codecpar->format == AV_PIX_FMT_PAL8) {
-            int size;
-            void *palette = av_packet_get_side_data(pkt, AV_PKT_DATA_PALETTE, &size);
-
-            if (!palette) {
-                av_log(s, AV_LOG_ERROR, "PAL8 packet is missing palette in extradata\n");
-                return AVERROR_INVALIDDATA;
-            }
-            if (size != AVPALETTE_SIZE) {
-                av_log(s, AV_LOG_ERROR, "Invalid palette extradata\n");
-                return AVERROR_INVALIDDATA;
-            }
-            gif_image_write_header(s->pb, video_st, gif->loop, palette);
+    if (!gif->last_pos) {
+        int delay_pos;
+        int off = 13;
+
+        if (pkt->size < 13)
+            return AVERROR(EINVAL);
+
+        if (pkt->data[10] & 0x80)
+            off += 3 * (1 << ((pkt->data[10] & 0x07) + 1));
+
+        if (pkt->size < off + 2)
+            return AVERROR(EINVAL);
+
+        avio_write(pb, pkt->data, off);
+
+        if (pkt->data[off] == GIF_EXTENSION_INTRODUCER && pkt->data[off + 1] == 0xff)
+            off += 19;
+
+        if (pkt->size <= off)
+            return AVERROR(EINVAL);
+
+        /* "NETSCAPE EXTENSION" for looped animation GIF */
+        if (gif->loop >= 0) {
+            avio_w8(pb, GIF_EXTENSION_INTRODUCER); /* GIF Extension code */
+            avio_w8(pb, GIF_APP_EXT_LABEL); /* Application Extension Label */
+            avio_w8(pb, 0x0b); /* Length of Application Block */
+            avio_write(pb, "NETSCAPE2.0", sizeof("NETSCAPE2.0") - 1);
+            avio_w8(pb, 0x03); /* Length of Data Sub-Block */
+            avio_w8(pb, 0x01);
+            avio_wl16(pb, (uint16_t)gif->loop);
+            avio_w8(pb, 0x00); /* Data Sub-block Terminator */
         }
 
-        return av_packet_ref(gif->prev_pkt, pkt);
+        delay_pos = gif_parse_packet(s, pkt->data + off, pkt->size - off);
+        if (delay_pos > 0 && delay_pos < pkt->size - off - 2) {
+            avio_write(pb, pkt->data + off, delay_pos);
+            avio_wl16(pb, gif_get_delay(gif, pkt, new_pkt));
+            avio_write(pb, pkt->data + off + delay_pos + 2, pkt->size - off - delay_pos - 2);
+        } else {
+            avio_write(pb, pkt->data + off, pkt->size - off);
+        }
+    } else {
+        int delay_pos = gif_parse_packet(s, pkt->data, pkt->size);
+
+        if (delay_pos > 0 && delay_pos < pkt->size - 2) {
+            avio_write(pb, pkt->data, delay_pos);
+            avio_wl16(pb, gif_get_delay(gif, pkt, new_pkt));
+            avio_write(pb, pkt->data + delay_pos + 2, pkt->size - delay_pos - 2);
+        } else {
+            avio_write(pb, pkt->data, pkt->size);
+        }
     }
-    return flush_packet(s, pkt);
+
+    av_packet_unref(gif->prev_pkt);
+    if (new_pkt)
+        return av_packet_ref(gif->prev_pkt, new_pkt);
+
+    return 0;
 }
 
 static int gif_write_trailer(AVFormatContext *s)
@@ -216,9 +174,11 @@ static int gif_write_trailer(AVFormatContext *s)
     GIFContext *gif = s->priv_data;
     AVIOContext *pb = s->pb;
 
-    flush_packet(s, NULL);
-    av_freep(&gif->prev_pkt);
-    avio_w8(pb, 0x3b);
+    gif_write_packet(s, NULL);
+
+    if (!gif->have_end)
+        avio_w8(pb, GIF_TRAILER);
+    av_packet_free(&gif->prev_pkt);
 
     return 0;
 }