Add stream_path to avm_frame.proto

tools/extract_proto/avm_frame.proto

diff --git a/tools/extract_proto/avm_frame.proto b/tools/extract_proto/avm_frame.proto
index abb1852..a448d44 100644
--- a/tools/extract_proto/avm_frame.proto
+++ b/tools/extract_proto/avm_frame.proto
@@ -238,13 +238,14 @@
   string stream_hash = 1;
   string stream_name = 2;
   float frame_rate = 3;
-  // Note: these are present both here and in FrameParms. For most streams we
+  // Note: these are present both here and in FrameParams. For most streams we
   // care about, the frame dimensions will be the same across every frame. For
   // streams with variable-sized frames, these fields can be omitted.
   int32 width = 4;
   int32 height = 5;
   string avm_version = 6;
   map<string, string> encoder_args = 7;
+  string stream_path = 8;
 }
 
 message TipFrameParams {

tools/extract_proto/extract_proto.cc

diff --git a/tools/extract_proto/extract_proto.cc b/tools/extract_proto/extract_proto.cc
index a06982f..2dffd87 100644
--- a/tools/extract_proto/extract_proto.cc
+++ b/tools/extract_proto/extract_proto.cc
@@ -93,6 +93,10 @@
           "Print progress as each frame is decoded.");
 ABSL_FLAG(bool, ignore_y4m_header, false,
           "Ignore dimensions and colorspace in Y4M header.");
+ABSL_FLAG(int, preserve_stream_path_depth, 0,
+          "Preserve this many levels of directory hierarchy of the stream's "
+          "path. -1 will preserve the entire absolute path. 0 will keep only "
+          "the filename. 1 will keep just the direct parent, etc...");
 
 namespace {
 constexpr std::string_view kY4mFrameMarker = "FRAME\n";
@@ -130,6 +134,7 @@
   std::ifstream *orig_yuv_file;
   int orig_yuv_bit_depth;
   std::filesystem::path stream_path;
+  int preserve_stream_path_depth;
   int decode_count;
   bool is_y4m_file;
   std::optional<Y4mHeader> y4m_header;
@@ -894,6 +899,23 @@
   aom_codec_control(&ctx->codec, AV1_SET_INSPECTION_CALLBACK, &ii);
 }
 
+void PopulateStreamPath(ExtractProtoContext *ctx) {
+  auto absolute_path = std::filesystem::absolute(ctx->stream_path);
+  std::filesystem::path relative_path;
+  if (ctx->preserve_stream_path_depth == -1) {
+    relative_path = absolute_path;
+  } else {
+    int index = std::distance(absolute_path.begin(), absolute_path.end());
+    for (const auto &part : absolute_path) {
+      index -= 1;
+      if (index <= ctx->preserve_stream_path_depth) {
+        relative_path /= part;
+      }
+    }
+  }
+  ctx->stream_params->set_stream_path(relative_path.make_preferred());
+}
+
 absl::Status OpenStream(ExtractProtoContext *ctx) {
   ctx->reader = aom_video_reader_open(ctx->stream_path.c_str());
   if (ctx->reader == nullptr) {
@@ -909,6 +931,7 @@
   LOG(INFO) << "Using " << aom_codec_iface_name(decoder);
   ctx->stream_params->set_avm_version(aom_codec_iface_name(decoder));
   ctx->stream_params->set_stream_name(ctx->stream_path.filename());
+  PopulateStreamPath(ctx);
   if (aom_codec_dec_init(&ctx->codec, decoder, nullptr, 0)) {
     return absl::InternalError("Failed to initialize decoder.");
   }
@@ -1034,6 +1057,8 @@
     .orig_yuv_file = have_orig_yuv ? &orig_yuv_file : nullptr,
     .orig_yuv_bit_depth = orig_yuv_bit_depth,
     .stream_path = stream_path,
+    .preserve_stream_path_depth =
+        absl::GetFlag(FLAGS_preserve_stream_path_depth),
     .decode_count = 0,
     .is_y4m_file = is_y4m_file,
     .y4m_header = y4m_header,