avcodec/hap: add "compressor" option to Hap encoder to disable secondary compression

The secondary compression in Hap is optional, this change exposes that option to
the user as some use-cases favour higher bitrate files to reduce workload
decoding.
Adds "none" or "snappy" as options for "compressor". Selecting "none" disregards
"chunks" option: chunking is only of benefit decompressing Snappy.

Reviewed-by: Martin Vignali <martin.vignali@gmail.com>
Signed-off-by: Tom Butterworth <bangnoise@gmail.com>

libavcodec/hap.h

@@ -65,6 +65,7 @@ typedef struct HapContext {
 
     enum HapTextureFormat opt_tex_fmt; /* Texture type (encoder only) */
     int opt_chunk_count; /* User-requested chunk count (encoder only) */
+    int opt_compressor; /* User-requested compressor (encoder only) */
 
     int chunk_count;
     HapChunk *chunks;

libavcodec/hapenc.c

@@ -204,15 +204,25 @@ static int hap_encode(AVCodecContext *avctx, AVPacket *pkt,
     if (ret < 0)
         return ret;
 
-    /* DXTC compression. */
-    ret = compress_texture(avctx, ctx->tex_buf, ctx->tex_size, frame);
-    if (ret < 0)
-        return ret;
-
-    /* Compress (using Snappy) the frame */
-    final_data_size = hap_compress_frame(avctx, pkt->data + header_length);
-    if (final_data_size < 0)
-        return final_data_size;
+    if (ctx->opt_compressor == HAP_COMP_NONE) {
+        /* DXTC compression directly to the packet buffer. */
+        ret = compress_texture(avctx, pkt->data + header_length, pkt->size - header_length, frame);
+        if (ret < 0)
+            return ret;
+
+        ctx->chunks[0].compressor = HAP_COMP_NONE;
+        final_data_size = ctx->tex_size;
+    } else {
+        /* DXTC compression. */
+        ret = compress_texture(avctx, ctx->tex_buf, ctx->tex_size, frame);
+        if (ret < 0)
+            return ret;
+
+        /* Compress (using Snappy) the frame */
+        final_data_size = hap_compress_frame(avctx, pkt->data + header_length);
+        if (final_data_size < 0)
+            return final_data_size;
+    }
 
     /* Write header at the start. */
     hap_write_frame_header(ctx, pkt->data, final_data_size + header_length);
@@ -273,10 +283,30 @@ static av_cold int hap_init(AVCodecContext *avctx)
     ctx->tex_size   = FFALIGN(avctx->width,  TEXTURE_BLOCK_W) *
                       FFALIGN(avctx->height, TEXTURE_BLOCK_H) * 4 / ratio;
 
-    /* Round the chunk count to divide evenly on DXT block edges */
-    corrected_chunk_count = av_clip(ctx->opt_chunk_count, 1, HAP_MAX_CHUNKS);
-    while ((ctx->tex_size / (64 / ratio)) % corrected_chunk_count != 0) {
-        corrected_chunk_count--;
+    switch (ctx->opt_compressor) {
+    case HAP_COMP_NONE:
+        /* No benefit chunking uncompressed data */
+        corrected_chunk_count = 1;
+
+        ctx->max_snappy = ctx->tex_size;
+        ctx->tex_buf = NULL;
+        break;
+    case HAP_COMP_SNAPPY:
+        /* Round the chunk count to divide evenly on DXT block edges */
+        corrected_chunk_count = av_clip(ctx->opt_chunk_count, 1, HAP_MAX_CHUNKS);
+        while ((ctx->tex_size / (64 / ratio)) % corrected_chunk_count != 0) {
+            corrected_chunk_count--;
+        }
+
+        ctx->max_snappy = snappy_max_compressed_length(ctx->tex_size / corrected_chunk_count);
+        ctx->tex_buf = av_malloc(ctx->tex_size);
+        if (!ctx->tex_buf) {
+            return AVERROR(ENOMEM);
+        }
+        break;
+    default:
+        av_log(avctx, AV_LOG_ERROR, "Invalid compresor %02X\n", ctx->opt_compressor);
+        return AVERROR_INVALIDDATA;
     }
     if (corrected_chunk_count != ctx->opt_chunk_count) {
         av_log(avctx, AV_LOG_INFO, "%d chunks requested but %d used.\n",
@@ -286,12 +316,6 @@ static av_cold int hap_init(AVCodecContext *avctx)
     if (ret != 0)
         return ret;
 
-    ctx->max_snappy = snappy_max_compressed_length(ctx->tex_size / corrected_chunk_count);
-
-    ctx->tex_buf  = av_malloc(ctx->tex_size);
-    if (!ctx->tex_buf)
-        return AVERROR(ENOMEM);
-
     return 0;
 }
 
@@ -312,6 +336,9 @@ static const AVOption options[] = {
         { "hap_alpha", "Hap Alpha (DXT5 textures)", 0, AV_OPT_TYPE_CONST, { .i64 = HAP_FMT_RGBADXT5  }, 0, 0, FLAGS, "format" },
         { "hap_q",     "Hap Q (DXT5-YCoCg textures)", 0, AV_OPT_TYPE_CONST, { .i64 = HAP_FMT_YCOCGDXT5 }, 0, 0, FLAGS, "format" },
     { "chunks", "chunk count", OFFSET(opt_chunk_count), AV_OPT_TYPE_INT, {.i64 = 1 }, 1, HAP_MAX_CHUNKS, FLAGS, },
+    { "compressor", "second-stage compressor", OFFSET(opt_compressor), AV_OPT_TYPE_INT, { .i64 = HAP_COMP_SNAPPY }, HAP_COMP_NONE, HAP_COMP_SNAPPY, FLAGS, "compressor" },
+        { "none",       "None", 0, AV_OPT_TYPE_CONST, { .i64 = HAP_COMP_NONE }, 0, 0, FLAGS, "compressor" },
+        { "snappy",     "Snappy", 0, AV_OPT_TYPE_CONST, { .i64 = HAP_COMP_SNAPPY }, 0, 0, FLAGS, "compressor" },
     { NULL },
 };